This conference focuses on the most recent advances in nonlinear optics and its applications.

The objective is to update the research and applications in the field providing a forum for discussion and interaction for all scientists, researchers, and engineers interested in the new results in the field of nonlinear optics.

Papers describing advances in every aspect of nonlinear optics and its applications particularly, but not limited, within the following areas are welcome:

  • nonlinear, ultrafast, and quantum plasmonics
  • nonlinear effects in non-homogeneous and nanoscale structures
  • organic and inorganic nonlinear materials
  • special nonlinear sources (parametric, up- and down-conversion, single photons) from X-rays to Terahertz
  • quantum optics in nonlinear processes
  • nonlinear devices for applications
  • nonlinear imaging systems and applications
  • novel nonlinear materials, including plasmonic and engineered structures
  • nonlinear spectroscopy and microscopy
  • ultrafast nonlinear optics
  • high-field nonlinear optics
  • modeling and simulations of nonlinear processes.
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    Conference 11770

    Nonlinear Optics and Applications XII

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    View Session ∨
    • Special Focus: Three Pillars of ELI Research Infrastructure-World's Most Advanced Short-pulse Lasers
    • Welcome and Monday Plenary Presentation I
    • Monday Plenary Presentation II
    • Tuesday Plenary Presentation III
    • Thursday Plenary Presentation VI
    • Wednesday Plenary Presentation V
    • Thursday Plenary Presentation VI
    • 1: Plasmonics
    • 2: Nonlinearities
    • 3: Raman
    • 4: Quadratic Materials
    • 5: Materials
    • 6: Applications
    • Poster Session
    Special Focus: Three Pillars of ELI Research Infrastructure-World's Most Advanced Short-pulse Lasers
    Livestream: 19 April 2021 • 09:00 - 11:05 CEST | Zoom



    9:00 to 9:05
    Welcome and Introduction
    Bedřich Rus, ELI Beamlines, Institute of Physics of the CAS (Czech Republic)
    Symposium Chair

    This event occurred in the past.
    Click
    here for Status of lasers and experiments at ELI-Beamlines
    here for ELI ALPS: the next generation of attosecond sources
    here for Status of high-power lasers and experiments at ELI-Nuclear Physics, Romania
    to now view in the SPIE Digital Library.
    11777-501
    Author(s): Georg Korn, ELI Beamlines (Czech Republic)
    On demand | Presented Live 19 April 2021
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    We are reviewing the high-average and high peak-power fs-laser sources and experimental areas currently in operation and preparation for user operation. This includes the 1 kHz, 15fs, 50mJ, Allegra laser based on OPCPA-technology. Short pulse 5ps-CPA thin disc lasers pump a series of OPCPA crystals ensuring a high contrast output. The Allegra laser enters the experimental area E1 with a number of end-stations for user experiments. The HAPLS (sub-30fs, Ti: Sapphire) laser pumped by a high-average power frequency converted DPSSL is currently delivering 500 TW, 3.3 Hz pulses via a stable vacuum beam transport system with a pointing stability around 1rad to the experimental areas for plasma physics experiments (E3) and ion acceleration (E4) with the ELIMAIA station. Both areas are fully equipped with target chambers and focusing optics for experimental operation and user assisted commissioning. The Nd:Glass laser Aton provides 1.5 kJ pulses and is currently being compressed to 10 PW in a large compressor tank. A second oscillator allows shaped pulse ns-operation at kJ level or future combination of 1 PW pulses and kJ shaped ns-pulses for advanced WDM or fusion experiments in the E3 area. A new laser disc liquid cooling technology enables repetition rates of 1 shot/minute allowing a much higher data acquisition for this kind of experiments. Furthermore we will report on the first experiments and the future experimental plans as well as on the prospects for user operation.
    11777-502
    Author(s): Katalin G. Varju, Univ. of Szeged (Hungary)
    On demand | Presented Live 19 April 2021
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    The Extreme Light Infrastructure – Attosecond Light Pulse Source (ELI-ALPS), the Hungarian pillar of ELI, is the first of its kind that operates by the principle of a user facility, supporting laser based fundamental and applied researches in physical, biological, chemical, medical and materials sciences at extreme short time scales. This goal is realized by the combination of specialized primary lasers which drive nonlinear frequency conversion and acceleration processes in more than twelve different secondary sources. Any light pulse source can act as a research tool by itself or, with femtosecond synchronization, in combination with any other of the sources. Thus a uniquely broad spectral range of the highest power and shortest light pulses becomes available for the study of dynamic processes on the attosecond time scale in atoms, molecules, condensed matter and plasmas. The ground-breaking laser systems together with the subsequent outstanding secondary sources generate the highest possible peak power at the highest possible repetition rate in a spectral range from the E-UV through visible and near infrared to THz. The facility – besides the regular scientific staff - will provide accessible research infrastructure for the international scientific community user groups from all around the world. The attosecond secondary sources are based on advanced techniques of Higher-order Harmonic Generation (HHG). Other secondary sources provide particle beams for plasma physics and radiobiology. A set of state-of-the-art endstations will be accessible to those users who do not have access or do not wish to bring along their own equipment. Step by step the lasers are now commissioned, trialed and handed over for user operation. References S. Kuhn et al., “The ELI-ALPS facility: the next generation of attosecond sources.”, Topical Review, Journal of Physics B, 50 (2017) 132002
    11777-503
    Author(s): Kazuo A. Tanaka, Extreme Light Infrastructure Nuclear Physics (Romania)
    On demand | Presented Live 19 April 2021
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    Founded by the European Strategy Forum on Research Infrastructure (ESFRI), three state-of-art laser-based institutes in Romania, Hungary, and the Czech Republic were commissioned in the Extreme Light Infrastructure (ELI). Construction for the three sites started in 2012 and, as of 2020, all sites are operational. ELI-NP (Extreme Light Infrastructure: Nuclear Physics) is located 10km south of Bucharest in Romania. Its flagship installation is two beams of 10 PW, each providing 230 J output energy at a 23 fs laser pulse width. The capability to provide a 10 PW output was recently demonstrated in a live performance. We were able to show that the 10 PW laser shots can be delivered for 10 minutes at a rate of one shot every minute. A total of 230 Zoom participants worldwide, including Prof G Mourou and Prof D Strickland, the Physics Nobel Laureates in 2018, witnessed this breakthrough demonstration. An early experiment at the 100 TW laser station at ELI-NP has already been completed. We successfully demonstrated an electron acceleration of up to 300 MeV, either resulting in monoenergetic or broadband spectra, depending on the well controllable experimental conditions we set. Operations at the 1 PW and 10 PW experimental stations will start soon. External user access will be tested with the early and commissioning experiments and will be formulated coherently within the framework of the IMPULSE project guided by ELI-DC. Reference Current status and highlights of the ELI-NP program research program, KA Tanaka, K Spohr, D Balabanski, et al., Matter Rad. Extremes, 5, 024402 (2020): doi.10.1063/1.5093535
    Session PL1: Welcome and Monday Plenary Presentation I
    Livestream: 19 April 2021 • 15:00 - 16:00 CEST | Zoom
    Monday Plenary Presentation I and Monday Plenary Presentation II are part of the same webinar session with a break in between.

    Times for this live event are all Central European Summer Time, CEST (UTC+2:00 hours)


    Welcome and Opening Remarks
    Bedřich Rus, ELI Beamlines, Institute of Physics of the CAS (Czech Republic)

    This event occurred in the past. Click here to now view in the SPIE Digital Library.
    11775-601
    New technologies for new astronomy (Plenary Presentation)
    Author(s): John C. Mather, NASA Goddard Space Flight Ctr. (United States)
    On demand | Presented Live 19 April 2021
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    We’ve come a long way since 1609, from spectacle lenses to mirrors in space, from twitching frog legs to the Event Horizon Telescope observing a black hole. But far more is possible. On the ground, a new generation of optical telescopes is under construction, up to 39 m in diameter. Adaptive optics compensates for the turbulent atmosphere, but could work far better with an orbiting reference beacon in space. Bright chemiluminescent emission lines in the upper atmosphere interfere with observations, but could be blocked by fiber optic filters. Energy-resolving photon counting detectors promise far greater sensitivity. New ways of making mirrors offer far better resolution for space X-ray telescopes. Coronagraphs can suppress starlight enough to reveal exoplanets in direct imaging, or starshades can cast star shadows on telescopes to do the same thing. New generations of far IR detectors with large cryogenic telescopes in space can reveal the cool and cold universe. Radio telescopes on the quiet far side of the Moon can overcome the limits of the ionosphere and intense local interference to see events in the early universe as it heated up again after the Big Bang expansion cooled everything. Neutrino telescopes can see stars being shredded by black holes, and gravitational wave detectors see merging neutron stars and black holes. Atom wave gravimeters can measure the internal structure of planets and asteroids, and sample return missions are already bring back distant bits of the solar system. What will happen next? I don’t know but it will be glorious.
    Session PL2: Monday Plenary Presentation II
    Livestream: 19 April 2021 • 17:00 - 18:00 CEST | Zoom
    Monday Plenary Presentation I and Monday Plenary Presentation II are part of the same webinar session with a break in between.

    Times for this live event are all Central European Summer Time, CEST (UTC+2:00 hours)


    Welcome and Introduction
    Ivo Rendina, CNR/Istituto per la Microelettronica e Microsistemi (Italy)
    Symposium Chair

    This event occurred in the past. Click here to now view in the SPIE Digital Library.
    11770-602
    Author(s): Anna C. Peacock, Univ. of Southampton (United Kingdom)
    On demand | Presented Live 19 April 2021
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    The nascent field of semiconductor core fibres is attracting increased interest as a means to exploit the excellent optical and optoelectronic functionality of the semiconductor material directly within the fibre geometry. Compared to their planar counterparts, this new class of waveguide retains many advantageous properties of the fibre platforms such as flexibility, cylindrical symmetry, and long waveguide lengths. Furthermore, owing to the robust glass cladding it is also possible to employ standard fibre post-processing procedures to tailor the waveguide dimensions and reduce the optical losses over a broad wavelength range, of particular use for nonlinear applications. This presentation will review progress in the development of nonlinear devices from the semiconductor core fibre platform and outline exciting future prospects for the field.
    Session PL3: Tuesday Plenary Presentation III
    Livestream: 20 April 2021 • 15:00 - 16:00 CEST | Zoom
    Times for this live event are all Central European Summer Time, CEST (UTC+2:00 hours)


    Welcome and Introduction
    Saša Bajt, Deutsches Elektronen-Synchrotron (Germany)
    Symposium Chair
    11776-603
    Author(s): Nina Rohringer, Max-Planck-Institut für Physik komplexer Systeme (Germany)
    On demand | Presented Live 20 April 2021
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    X-ray free-electron lasers, delivering x-ray pulses of femtosecond duration, are available for experiments for more than a decade and allow for hitherto unachievable x-ray intensities on sample, reaching up to 1021 W/cm2 for hard x-rays. At these intensities, the probability of a single atom or molecule to absorb a photon of an impinging x-ray pulse reaches unity. Moreover, several interactions of photons and matter within the duration of the x-ray pulse – nonlinear x-ray matter interactions – become possible, opening the pathway to nonlinear x-ray optics. For a macroscopic ensemble of atoms, molecules, nanometer-sized clusters or a solid, the interaction with a strongly focused x-ray beam can create macroscopic, highly excited states of matter, far from equilibrium. In particular, saturated absorption with a high-intensity x-ray pulse can result in transient states, present for roughly one femtosecond, with the characteristic feature, that every single atom in the interaction region is in a population inverted state with missing population in the innermost electronic shell. This macroscopic population inversion can lead to collective radiative decay mechanisms, such as amplified spontaneous emission or superfluorescence. In this presentation I will give you an overview over our experimental and theoretical investigations of these single-pass x-ray laser amplifiers in the x-ray spectral domain. I will address applications of this phenomenon in the area of chemical x-ray emission spectroscopy, a new concept of an x-ray laser oscillator, and will highlight recent theoretical developments to describe collective spontaneous emission in the x-ray spectral domain.
    Session PL4: Thursday Plenary Presentation VI
    Livestream: 22 April 2021 • 09:00 - 10:00 CEST | Zoom
    Times for this live event are all Central European Summer Time, CEST (UTC+2:00 hours)


    Welcome and Introduction
    Saša Bajt, Deutsches Elektronen-Synchrotron (Germany)
    Symposium Chair
    11776-606
    New research opportunities with FELs (Plenary Presentation)
    Author(s): Claudio Masciovecchio, Elettra-Sincrotrone Trieste S.C.p.A. (Italy)
    On demand | Presented Live 22 April 2021
    Session PL5: Wednesday Plenary Presentation V
    Livestream: 21 April 2021 • 17:00 - 18:00 CEST | Zoom
    Times for this live event are all Central European Summer Time, CEST (UTC+2:00 hours)

    Welcome and Introduction
    Ivo Rendina, CNR/Istituto per la Microelettronica e Microsistemi (Italy)
    Symposium Chair
    11775-605
    Author(s): Mona Jarrahi, UCLA Samueli School of Engineering (United States)
    On demand | Presented Live 21 April 2021
    Session PL6: Thursday Plenary Presentation VI
    Livestream: 22 April 2021 • 09:00 - 10:00 CEST | Zoom
    Times for this live event are all Central European Summer Time, CEST (UTC+2:00 hours)


    Welcome and Introduction
    Saša Bajt, Deutsches Elektronen-Synchrotron (Germany)
    Symposium Chair
    11776-606
    New research opportunities with FELs (Plenary Presentation)
    Author(s): Claudio Masciovecchio, Elettra-Sincrotrone Trieste S.C.p.A. (Italy)
    On demand | Presented Live 22 April 2021
    Session 1: Plasmonics
    11770-1
    Author(s): Ventsislav Kolev Valev, Univ. of Bath (United Kingdom)
    On demand
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    This talk will focus on three absorbing lines of research into nanophotonics. It will begin with the first experimental observation of a chiroptical effect that was predicted 40 years ago.[1,2] Our team recently demonstrated that in chiral metal nanoparticles (those that lack mirror symmetry) the intensity of light, scattered at the secondharmonic frequency, is proportional to the chirality. This effect was predicted 40 years ago, it is >10,000 more sensitive than corresponding linear optical effects and it could enable safer pharmaceuticals. Next, it will consider the smallest backjets (‘nanojets’) ever created and will discuss how they can serve to assemble novel metamaterials based on nano metalworking.[3,4] Nano metalworking is an exciting, emerging field that is largely unexplored. Finally, it will illustrate how a vapour stabilization technique can greatly enhance quantum sensors.[5] REFERENCES [1] Phys Rev. X 9, 011024 (2019). [2] J. Chem. Phys. 70, 1027 (1979). [3] Adv. Mater. 24, OP29-OP35 (2012). [4] Nat. Commun. 5, 4568 (2014). [5] Nat. Commun. 10, 2328 (2019).
    11770-2
    Author(s): Lukas Ohnoutek, Ventsislav K. Valev, Univ. of Bath (United Kingdom)
    On demand
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    Chirality, i.e. the lack of mirror symmetry of objects, is attracting a significant amount of interest due to the importance of chiral molecules and nanostructures in pharmaceuticals and in nanotechnological applications. Current methods of characterising this chirality often rely on linear optical methods that lack sensitivity. In this work, we demonstrate the extreme sensitivity of second harmonic hyper-Rayleigh scattering optical activity (HRS OA), which allows us to distinguish between two chiral forms of gold nanoparticles while detecting signal from a volume containing a single nanoparticle, on average.[1] We study gold cuboids with crystallographic chirality (“helicoids”) floating freely in a liquid. We illuminate the helicoids with fs laser pulses at 730 nm and measure light scattered at 365 nm. We find that the intensity of the 365-nm light depends on the direction of incident circularly polarized light and on the chirality of the helicoids. Crucially, our illumination volume is only ≈30 μm3, where the concentration of the nanoparticles is down to a single helicoid, and even lower. In summary, we demonstrate that HRS OA can determine the chirality of single nanoparticles. Our results illustrate the huge sensitivity of the technique for hyper-sensitive chiroptical characterization. [1] L. Ohnoutek et al., “Single Nanoparticle Chiroptics in a Liquid: Optical Activity in Hyper-Rayleigh Scattering from Au Helicoids,” Nano Lett., acs.nanolett.0c01659 (2020).
    11770-3
    Author(s): Álvaro Rodríguez Echarri, ICFO - Institut de Ciències Fotòniques (Spain); Joel D. Cox, Univ. of Southern Denmark (Denmark); F. Javier García de Abajo, ICFO - Institut de Ciències Fotòniques (Spain), Institució Catalana de Recerca i Estudis Avançats (Spain)
    On demand
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    Graphene nanoribbons provide the means to excite surface plasmon upon direct excitation, avoiding then the momentum mismatch in extended graphene. We describe those collective modes employing a rigorous quantum-mechanical simulation, which accounts for nonlocal, quantum finite-size, and edge-termination effects manifested in the optical response. Our simulations reveal a strong dependence on such phenomena for excitation with a high optical momentum component along the direction of transverse symmetry in both the linear and nonlinear optical response, wherein particular second-order nonlinear phenomena are found to manifest with high efficiency due to the breaking of inversion symmetry. These results can be employed to describe emitters, as two-level atoms, close by used to excite and determine the nonlinear dynamics originated by those plasmons in the graphene nanoribbons.
    11770-4
    Author(s): Álvaro Rodríguez Echarri, Fadil Iyikanat, ICFO - Institut de Ciències Fotòniques (Spain); Joel D. Cox, Univ. of Southern Denmark (Denmark); F. Javier García de Abajo, ICFO - Institut de Ciències Fotòniques (Spain), Institució Catalana de Recerca i Estudis Avançats (Spain)
    On demand
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    Atomically thin films possess appealing intrinsic properties for nonlinear optics that we explore employing a rigorous quantum-mechanical description. The main optical response is driven by plasmons, the collective oscillation of conduction electrons, which are modeled through the proper consideration of the dominant features of their electronic band structure, including surface and quantum well states along with the bandgap arising for each crystallographic facet. We report a beneficial use of films decreasing in thickness down to few-atom-thick sizes, influencing both the linear and the nonlinear optical response. Such a degree of tunability makes them unique together with lower losses compared to their amorphous counterparts. These results facilitate the development of atomically-thin nonlinear nanophotonic devices based on well-defined crystalline metal films.
    Session 2: Nonlinearities
    11770-10
    Author(s): Aleksei A. Kalinovich, Maria V. Komissarova, Sergey V. Sazonov, Irina G. Zakharova, M. V. Lomonosov Moscow State Univ. (Russian Federation)
    On demand
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    Any non-centrosymmetric material always has its own third order nonlinearity. Provided high intensity of input signal this nonlinearity becomes important along with the main second-order one. Influence of the cubic nonlinearity on the second harmonic generation is well studied either for wave packets or for wave beams. However, simultaneous account of spatial and temporal effects for combined nonlinearity is a rather complicated task since under certain conditions the competition between two nonlinearities may be crucial. Our studies are focused on high intensity spatiotemporal parametric processes in a microdispersive medium. We solve analytically and numerically the system of coupled parabolic equations for second harmonic generation that are supplemented with terms responsible for self- and cross- modulations. Joint influence of quadratic and cubic nonlinearities is studied for the case of anomalous dispersion at both frequencies. Recently it was demonstrated that provided small phase mismatches a stable two-color light bullet may be generated and propagates in a medium with pure quadratic nonlinearity. At the same time pure Kerr nonlinearity is responsible for bullet instability. In our investigations we reveal a threshold condition of the two-color bullet stability in the medium with combined quadratic-cubic nonlinearity. Our analytical estimations are confirmed by numerical simulations which cover a wide range of phase and group-velocity mismatch values.
    11770-11
    Author(s): Aleksei A. Kalinovich, Boris S. Bryantsev, Maria V. Komissarova, Sergey V. Sazonov, Irina G. Zakharova, M. V. Lomonosov Moscow State Univ. (Russian Federation)
    On demand
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    Recently a possibility of the formation of “dancing” light bullets was analytically shown in graded-index waveguides with both Kerr and quadratic nonlinearities (Sazonov S.V., Phys.Rev. A (2019), Sazonov S.V., Laser Phys. Lett. (2020)). At that, a two-color “dancing” light bullet in a quadratic nonlinear waveguide may form at both anomalous and normal group velocity dispersion at the fundamental frequency. Here and in what follows we refer as “dancing” light (optical) bullets spatiotemporal solitons whose trajectories can be spatial Lissajous figures with anisotropic spatial distribution of the refractive index in the cross section of the waveguide. Stability of a two-color “dancing” light bullet was theoretically demonstrated without additional conditions for its temporal duration, aperture, and power. These results were established with the help of the averaged Lagrangian method in the framework of the quasi-optical approach under the conditions of phase and group matching. The mentioned conditions are known to be hardly achievable in experiment. In the present work we study “dancing” light bullet generation by means of numerical simulation in the cases when only one of the conditions of synchronism is fulfilled. Besides, we make the simulation of the formation of a two-color “dancing” optical bullet under the process of second harmonic generation. In this case, a pulse containing only the main carrier frequency is launched into the input of the waveguide at an angle to its axis. We demonstrate that a pulse at the doubled frequency is generated in the waveguide, followed by the formation of the bound state of both harmonics representing a two-color “dancing” light bullet.
    11770-12
    Author(s): Nikita M. Kondratiev, Valery E. Lobanov, Evgeny Lonshakov, Nikita Dmitriev, Russian Quantum Ctr. (Russian Federation); Igor A. Bilenko, M.V. Lomonosov Moscow State Univ. (Russian Federation)
    On demand
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    The effect of the self-injection locking (SIL) is well-known for many years in the theory of oscillations, radiophysics and optics and is actively used for the stabilization and spectral purification of the corresponding generators. Last years it has attracted even more attention due to the possibility of using such stabilized lasers as pump sources for the realization of the nonlinear processes in the same microresonators, simultaneously used for laser linewidth reduction. However, existing linear theories of the self-injection locking unable to predict soliton generation because enough value of the pump frequency detuning can not be obtained in the linear regime. The development of full nonlinear theory becomes even more important, since recently generation of the solitonic pulses at normal group velocity dispersion has been demonstrated in the self-injection locking regime We developed an original model describing the process of the frequency comb generation in the self-injection locking regime and performed numerical simulation of this process. Generation of the dissipative Kerr solitons in the self-injection locking regime at anomalous group velocity dispersion was studied numerically. Different regimes of the soliton excitation depending on the locking phase, backscattering parameter and pump power were identified. It was also proposed and confirmed numerically that self-injection locking may provide an easy way for the generation of the frequency combs at normal group velocity dispersion. Generation of platicons was demonstrated and studied in detail. Parameter range providing platicon excitation was found.
    11770-13
    Author(s): Kirill L. Koshelev, ITMO Univ. (Russian Federation), The Australian National Univ. (Australia); George Zograf, ITMO Univ. (Russian Federation); Viacheslav Korolev, Friedrich-Schiller-Univ. Jena (Germany); Anastasia Zalogina, Duk-Yong Choi, The Australian National Univ. (Australia); Richard Hollinger, Institute of Optics and Quantum Electronics, Friedrich-Schiller-Univ. Jena (Germany); Barry Luther Davies, The Australian National Univ. (Australia); Michael Zurch, Institute of Optics and Quantum Electronics, Friedrich-Schiller Univ. Jena (Germany), Univ. of California (United States); Daniil Kartashov, Christian Spielmann, Institute of Optics and Quantum Electronics, Friedrich-Schiller Univ. Jena (Germany); Sergey Makarov, ITMO Univ. (Russian Federation); Sergey Kruk, The Australian National Univ. (Australia), Univ. Paderborn (Germany); Yuri Kivshar, The Australian National Univ. (Australia), ITMO Univ. (Russian Federation)
    On demand
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    Bound states in the continuum (BICs) represent non-radiative modes, received increased attention in optics and photonics as a simple tool to achieve giant quality factors (Q factors). For metasurfaces composed of subwavelength meta-atoms with broken in-plane symmetry, it was shown that Q factor of quasi-BICs can be unambiguously controlled by variation of meta-atom asymmetry parameter. The variation of the asymmetry parameter allows to achieve the optimal coupling condition that maximizes the fields inside the metasurface via matching the rates of radiative and non-radiative losses. Lower-order harmonics (such as 2nd and 3rd) have been observed in a variety of subwavelength systems starting from plasmonic nanoparticles, as well as in all-dielectric nanostructures with substantially enhanced efficiencies due to Mie resonances. Observing high-order harmonics in nanostructures is challenging due to low conversion efficiencies and has been little studied. Here, we report the observation of high-harmonic generation (HHG) in dielectric metasurfaces hosting BICs. The metasurface was composed of a square lattice with parallel Si bars of a slightly different width placed on a transparent substrate. The structure was engineered to support a quasi-BIC in the mid-IR with a high Q factor. We tuned the metasurface asymmetry to enable the optimal coupling condition that provide the highest high-harmonic generation efficiency. In the experiment, we demonstrated the generation of odd optical harmonics from the 3rd to the 11th order in the BIC regime and studied their polarization dependence. The concept of metasurfaces with highly localised light which is achieved by employing BIC resonances provides a new degree of freedom to control experimentally the nonlinear optical response.
    11770-14
    Author(s): Anton V. Zasedatelev, Univ. of Southampton (United Kingdom), Skolkovo Institute of Science and Technology (Russian Federation); Denis Sannikov, Timur Yagafarov, Anton Putintsev, Skolkovo Institute of Science and Technology (Russian Federation); Kyriacos Georgiou, David Lidzey, The Univ. of Sheffield (United Kingdom); Pavlos G. Lagoudakis, Skolkovo Institute of Science and Technology (Russian Federation), Univ. of Southampton (United Kingdom)
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    Bose-Einstein condensates of exciton-polaritons in inorganic semiconductor microcavities are known to possess strong interparticle interactions attributed to their excitonic component. The interactions play a crucial role in the nonlinear dynamics of such systems and can be witnessed as the high energy shift of polariton states. However, the localised nature of Frenkel excitons in strongly coupled organic microcavities precludes interparticle Coulomb exchange-interactions that affect nonlinear dynamics and change mechanisms of polariton energy shifts accordingly. We have scrutinized the origins of energy shifts in connection with nonlinear dynamics in Frenkel exciton-polariton condensates and examined the possible contributions: intracavity optical Kerr-effect, gain-induced frequency pulling, polariton interactions and effects related to saturation of optical transitions for "dark"- and "bright" molecules [1]. Unlike the conventional strongly coupled semiconductor microcavities, we have shown that nonlinear interactions within the condensate do not rely on polariton interactions but instead originated from Pauli-blocking principle forbidding double excitation of the same molecular states. We have developed a theoretical model explaining the omnipresent energy shift of the condensate wavefunction together with its spectral and polarization features at the BEC transition in a consistent way. The crucial role of intermolecular energy transfer and “dark” exciton reservoir has been demonstrated for the first time. We believe the principles explored in this work are relevant to other systems exhibiting strong coupling of Frenkel excitons with a cavity mode, regardless of a cavity type, whether one dealing with Fabry-Perot cavities or plasmonic nanocavities etc and; therefore, provide general insight on nonlinear phenomena in composite light-matter condensates. [1] T. Yagafarov, D. Sannikov, A. Zasedatelev, K. Georgiou, A. Baranikov, O. Kyriienko, I. Shelykh, L. Gai, Z. Shen, D. G. Lidzey, P. Lagoudakis, Mechanisms of blueshifts in organic polariton condensates, Commun Phys 3, 18 (2020). https://doi.org/10.1038/s42005-019-0278-6
    Session 3: Raman
    11770-15
    Author(s): Alexei M. Zheltikov, Mitrofanov Alexander, Dmitri A. Sidorov-Biryukov, Alexander A. Voronin, Rozhko Mikhail Viktorovich, Andrey B. Fedotov, M. V. Lomonosov Moscow State Univ. (Russian Federation)
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    Spectral analysis of high-order harmonics generated by ultrashort mid-infrared pulses in molecular nitrogen reveals well-resolved signatures of inverse Raman scattering, showing up near the frequencies of prominent vibrational transitions of nitrogen molecules. When tuned on a resonance with the vʹ = 0 → vʺ = 0 pathway within the B3Πg → C3Πu second positive system of molecular nitrogen, the eleventh harmonic of a 3.9-μm sub-80-fs driver is shown to acquire a distinctive antisymmetric spectral profile with red-shifted bright and blue-shifted dark features as indicators of stimulated Raman gain and loss. This high-harmonic setting extends the inverse Raman effect to a vast class of strong-field light–matter interaction scenarios.
    11770-16
    Author(s): Alexandr V. Mitrofanov, Dmitri A. Sidorov-Biryukov, Rozhko Mikhail Viktorovich, Alexander A. Voronin, Maxim Nazarov, Andrey B. Fedotov, Alexei M. Zheltikov, M. V. Lomonosov Moscow State Univ. (Russian Federation)
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    With the wavelength of a short-pulse laser driver shifted to the midinfrared range, the low-frequency output of laser-induced plasmas can be drastically enhanced, as our experiments show, providing a source of ultrabroadband radiation with a spectrum spanning across the entire terahertz, millimeter-wave, and microwave bands. At low gas pressures, such ultrabroadband field waveforms are shown to rapidly build up their coherence, developing a well-resolved emission cone, dominated by a radial radiation energy flux. As counterintuitive as it may seem, this behavior of the intensity, coherence, and polarization of the low-frequency plasma output is shown to be consistent with a physical scenario of Cherenkov-type radiation emission by ponderomotively driven plasma currents.
    11770-17
    Author(s): Weiqian Zhao, Southeast Univ. (China), Univ. of Southampton (United Kingdom); Chun Yang, Southeast Univ. (China); Ming Ya Shen, Yangzhou Univ. (China); Weijie Xu, Southeast Univ. (China)
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    A novel technique for THz signal generation by photomixing the ±1 order Kelly sidebands of a soliton ML fiber laser is proposed. The optical-to-THz conversion efficiency is improved significantly. This technique not only have advantages brought by soliton ML fiber laser, such as free from optical alignment and compactness, but also some essential advantages of using Kelly sidebands, such as phase-locked peak wavelengths and large peak intensity of ±1 order Kelly sidebands, and consequently, THz signal generation can be stable and efficient. A numerical model based on linear Yb-doped ML fiber laser is built to simulate and find optimal parameters for the Kelly sidebands. An inverse exponentially relationship between the total dispersion of laser cavity and spacing of the ±1 order sidebands is found. Other factors influencing the sidebands fractional power and bandwidth of Kelly sidebands are also investigated. In experiment, an Yb-doped linear-cavity mode-locking fiber laser is built and its optical spectrum is measured. By utilizing the obtained data of the optical spectrum, the generated THz spectrum is worked out. Strong THz signals appear at around 0.185THz which comes from photomixing the ±1 order sidebands with 1.03nm spacing. Another mode-locking laser with Er-doped fiber ring-cavity containing CFBG is constructed. The results show that the spacing of the ±1 order Kelly sidebands can vary from 15nm to 1.18nm, which corresponds to the frequency range of THz signals generated from 0.103THz to 1.44THz. The normalized intensities are about 0.07 and 0.01 respectively.
    11770-18
    Author(s): Dmitrii Przhiialkovskii, Oleg V. Butov, Kotelnikov Institute of Radio Engineering and Electronics (Russian Federation)
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    Fiber Bragg gratings are widely used in modern optoelectronic devices and fiber optics as narrow-band optical filters, mirrors for fiber lasers, as well as sensitive elements for various sensor systems. However, relatively low thermal and radiation resistance of standard fiber Bragg gratings appear to be considerable factors limiting their applications. To solve this problem, the method of point-by-point inscription of Bragg structures in a fiber by means of femtosecond laser radiation can be used. Due to the ultrashort pulse duration, such values of the electromagnetic field’s intensity are achieved in the focal point which make it possible to directly impact the regular silica glass network due to multiphoton processes. Despite the fact that the problems of the interaction of ultrashort pulsed radiation with matter have been studied for a long time, a unified generally accepted theory of the processes and phenomena occurring during such an interaction has not yet been formed. The study of the FBG parameters’ evolution during the very inscription process can make it possible to understand the processes and phenomena occurring during the inscription, and the variation of the parameters of the inscription radiation, such as the pulse duration and energy, can make it possible to better understand the features of the influence of certain radiation parameters on the resulting FBG inscription. This report presents the results of such a study and analyzes the data obtained. For the first time, a method of multi-pass point-by-point inscription of Bragg gratings was proposed. The proposed method of multi-pass FBG inscription solves not only an applied problem, namely FBG inscription with ultra-precise parameters by the Point-By-Point method, but also serves as a new tool for fundamental research.
    11770-20
    Author(s): Nikita Nekrasov, National Research Univ. of Electronic Technology (Russian Federation); Boris I. Afinogenov, Natalia G. Kokareva, Vladimir O. Bessonov, Fedyanin A. Andrey, Lomonosov Moscow State University (Russian Federation); Ivan I. Bobrinetskiy, National Research University of Electronic Technology (Russian Federation)
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    Possibility of femtosecond laser pulses to affect on materials modification takes a big part of interest in ultra-fast processes research and technology investigations. In case of graphene surface modification and functionalization using femtosecond laser there are many effects appears, such as ablation, covalent bonding of different chemical groups, re-crystallization in three-dimensional shapes. For graphene modification processes we used 80 MHz laser with 780 nm wavelength with different laser scanning speed. Exposure of graphene to femtosecond laser pulse is determined by the prevalence of physical or chemical effects during exposure to a laser pulse. The range of laser exposure was narrowed down to values causing the formation of atomic defects in the carbon lattice, which makes it possible to form nanopores in the graphene. By evaluating the intensity ratio of certain Raman spectra peaks, namely the G mode (~ 1600 1/cm) and D mode (~ 1350 1/cm), the degree of functionalization, or amorphization of graphene, was estimated. It was revealed that the ablation threshold begins to appear, starting from 18 mW and higher at an exposure speed in the range of 400-500 μm/s. In this case, the ablation threshold lies in a narrow range of radiation power within 1 mW. In this range, both graphene functionalization and a change in the graphene surface roughness were observed. Despite the change in the morphology of graphene, the graphene resistance fell by only ~4 times, and the controllability of the graphene transistor did not change its character much, showing a shift towards hole conductivity. The influence of the direction of polarization of optical radiation on the modification of graphene was also detected. The difference in parameters between the samples modified with different polarization directions along the direction of the beam motion can be explained as the interference interaction of the electron density in graphene.
    Session 4: Quadratic Materials
    11770-21
    Author(s): Rachel Grange, ETH Zurich (Switzerland)
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    Nonlinear and electro-optic devices are present in our daily life with many applications: light sources for microsurgery, green laser pointers, or modulators for telecommunication. They mainly use bulk materials such as glass fibers or high-quality crystals, hardly integrable or scalable due to low signal and difficult fabrication. Here I will show several strategies to enhance optical signals by engineering metal-oxides. First, I will explain some fundamental aspects of quadratic materials. Then, I will show several photonic systems relying on bottom-up assemblies of barium titanate nanoparticles either to obtain electro-optic metasurfaces or broadband Mie driven microspheres.
    11770-22
    Author(s): Emil Z. Ulsig, Nicolas Volet, Aarhus Univ. (Denmark)
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    This work presents an approach for continuous-wave (CW) laser emission in the far UVC (200-230 nm) using second-harmonic generation (SHG) in barium borate (BBO) thin-film waveguides. Modal phase matching (PhM) is employed, resulting in conversion efficiencies up to two orders of magnitude larger than current state of the art. The designs are based on commercially available thin-film BBO crystals, optically bonded to a substrate of ultra-violet fused silica (UVFS). BBO is a mature crystal, transparent for wavelengths down to 190 nm and exhibits a relatively large second-order nonlinear susceptibility.The crystal orientation is analytically considered for waveguides, and two designs with perfect modal PhM are simulated. The first design includes a BBO ridge-waveguide defined by dry etching. This allows for good confinement and spatial overlap of the relevant optical modes. The second design includes a strip-loaded waveguide, which aims at suppressing the side-wall scattering by confining the optical modes in the BBO thin-film. For both designs, the waveguide geometry is engineered to maximize the conversion efficiency with the constrain of perfect PhM and robustness to fabrication uncertainties. It is shown that the conversion efficiency can be greatly enhanced in BBO waveguides by using a PhM angle different from the one used in bulk. Fabrication proposals and tolerance analysis are provided, presenting a credible path towards a robust and efficient design for the nonlinear waveguide. Applications that would benefit from this compact UVC laser include absorption and Raman spectroscopies, along with germicidal systems.
    11770-23
    Author(s): Nikita M. Kondratiev, Ramzil R. Galiev, Valery E. Lobanov, Russian Quantum Ctr. (Russian Federation)
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    Self-injection locking is an effective tool of laser stabilization, known from the origins of radiophysics. Recently it was shown to be useful for perspective compact sources of optical frequency combs. This, however, implies the nonlinearity and high power inside the microresonator. Recently, we showed, that the account for the nonlinearity in the self-injection locking model substantially changes the system behaviour. However, thermal effects, inevitably arising from the high intracavity power, have not been considered yet. This point is also of great importance as these effects are known to be a serious obstacle for stable dissipative Kerr soliton generation. In this work we develop further the self-injection locking theory and show that thermal nonlinearity also introduce novel and important features. We analyse in detail several possible regimes arising due to thermal and Kerr nonlinearity competition and analyse tuning curves at different signs of thermorefractive coefficient. We confirm our predictions that the locking should help to overcome the temperature drift problem and show that nonlinear frequency shift helps to reach the desired detuning for the soliton comb state inside the locking band.
    11770-24
    Author(s): Ilya Orekhov, Stanislav G. Sazonkin, Kirill Bugai, Dmitriy A. Dvoretskiy, Dmitriy Shelestov, Kirill V. Koshelev, Roman Khan, Valeriy E. Karasik, Lev K. Denisov, Bauman Moscow State Technical Univ. (Russian Federation); Valeriy Davydov, Institute for High Pressure Physics (Russian Federation)
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    Currently, the effective generation of ultrashort pulses has been efficiently implemented using various mode-locking (ML) techniques. Among them various types of saturable absorbers (SA) based on semiconductor materials such as SESAM, topological insulators, black phosphorus-based SA, bismuthene SA, ReSe2, MoS2, SnS2 SAs, and other novel 2D optical materials have ultrafast saturable absorption at the infrared spectral region. One of the reliable methods of ML in a resonator can be attributed to the use of SAs based on various carbon nanostructures, such as single-wall carbon nanotubes (SWCNTs-SAs), graphene, and graphene oxide. In this paper, we have studied ML features in a sub-200-fs erbium-doped all-fiber laser based on a saturable absorber obtained by high-pressure-high-temperature treatment of commercially available SWCNTs. We have shown that there is a significant effect on the ultrafast optical properties of SA due to the well-aligned and high-density structure of newly-developed SWCNTs and related it to the ML laser performance. We have obtained a low-intensity-noise ultra-short stretched pulse generation with a repetition rate of 42.22 MHz, a spectral pulse width of 30 nm, and with an average output power of 12.5 mW with long-term stability < 0.4 % during 3 h measurement time.
    Session 5: Materials
    11770-25
    Author(s): Laura Rodriguez Sune, Univ. Politècnica de Catalunyaalunya (Spain); Jose Trull, Univ. Politècnica de Catalunya (Spain); Michael Scalora, U.S. Army Aviation and Missile Command, U.S. Army Combat Capabilities Development Command (United States); Neset Akozbek, AEgis Technologies Inc (United States); Crina M. Cojocaru, Univ. Politècnica de Catalunya (Spain)
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    The use of semiconductors, metals and conductive oxides in the process of fabrication of actual nano devices is at the front edge of nowadays technology, exploiting the properties of light propagation and localization at nanometric scale in new and surprising ways. At these scales the usual theory describing the nonlinear (NL) effects of electromagnetic fields should be revisited and analyzed. We report a collection of experimental results of nonlinear harmonic generation in different nanolayers: semiconductors, conductive oxides and metals. The comparison of these experimental results with numerical predictions of our theoretical model identifies, distinguishes and explains the different nonlinear contributions to the harmonics generated by these materials at nanoscale. Our model accounts for surface, magnetic and bulk nonlinearities arising from free and bound charges, preserving linear and nonlinear dispersion, nonlocal effects due to pressure and viscosity.
    11770-30
    Author(s): Laura Rodriguez Sune, Jose Trull, Crina M. Cojocaru, Univ. Politècnica de Catalunya (Spain); Neset Akozbek, The AEgis Technologies Group, Inc. (United States); Domenico de Ceglia, Univ. degli Studi di Padova (Italy); Maria Antonietta Vincenti, Univ. degli Studi di Brescia (Italy); Michael Scalora, Redstone Arsenal (United States)
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    Currently, nanostructures are routinely fabricated and integrated in different photonic devices for a variety of purposes and applications. For instance, in order to engineer properly nano-antennas or filters, it is important to understand accurately how light interacts with metals, semiconductors, or ordinary dielectrics at the nanoscale. When the nanoscale is reached, light-matter interactions can display new phenomena, conventional approximations may not always be applicable, and new strategies must be sought in order to study and understand light-matter interactions at the nanoscale. Some examples of nanoscale optical phenomena are nonlocal effects, electronic wave function spill-out, discontinuous surface charge densities at metal-metal and metal-conducting oxide interfaces, and quantum tunneling, to name a few. In this work, we present the study of two well-known nonlinear processes at the nanoscale, which are second and third harmonic generation. We report experimental results on second and third harmonic generation from 20nm- and 70nm-thick gold nanolayers, for TE- and TM-polarized incident light pulses. These measurements are compared with numerical simulations based on a microscopic hydrodynamic model which accounts for surface, magnetic and bulk nonlinearities arising from both free and bound charges, preserving linear and nonlinear dispersion, nonlocal effects due to pressure and viscosity, and an intensity dependent free electron density, to which we refer as hot electrons contribution. We also discuss and highlight the relative roles bound electrons and hot electrons play in third harmonic generation. While planar structures are generally the simplest to fabricate, metal layers that are only a few nanometers thick and partially transparent are almost never studied. Yet, they offer an additional reference point for comparison, i.e. transmission, which through relatively simple experimental measurements affords the opportunity to test the accuracy of available theoretical models at the nanoscale.
    11770-31
    Author(s): Attilio Zilli, Politecnico di Milano (Italy); Tommi Isoniemi, The Univ. of Sheffield (United Kingdom); Marzia Iarossi, Istituto Italiano di Tecnologia (Italy); Marco Finazzi, Politecnico di Milano (Italy); Francesco De Angelis, Istituto Italiano di Tecnologia (Italy); Michele Celebrano, Politecnico di Milano (Italy); Nicolò Maccaferri, Univ. du Luxembourg (Luxembourg)
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    We report efficient second-harmonic emission by single multilayer metal–dielectric nanocavities. Engineering the intrinsic interface-induced symmetry breaking by resonant optical absorption design, allows to achieve almost two orders of magnitude higher second-harmonic generation efficiency compared to gold nanostructures with the same geometry. We estimate a second-order nonlinear susceptibility of the order of 1 pm/V, which is comparable to widely used nonlinear crystals. We envision that our system, which combines the advantages of both plasmonic and dielectric materials, might enable the realization of composite nano-systems for an efficient multi-purpose manipulation of nonlinear optical processes at the nanoscale.
    11770-32
    Author(s): Ivan D. Laktaev, Kotelnikov Institute of Radio Engineering and Electronics (Russian Federation); Bedil M. Saidzhonov, Roman V. Vasiliev, M. V. Lomonosov Moscow State Univ. (Russian Federation); Aleksandr M. Smirnov, Oleg V. Butov, Kotelnikov Institute of Radio Engineering and Electronics (Russian Federation)
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    Nowadays, investigation of nonlinear optical properties of CdSe nanoplatelets is hot topic in 2D optical materials. These nanostructures possess unique optical characteristics, which are desirable for many practical application such as: gain medium for laser generation, solar cells, light emitting diodes and biomarkers. The problem of the second harmonic generation in the CdSe nanocrystals is one of the most important scientific problems. It was shown that the second harmonic can be used in nonlinear optical microscopy. The second harmonic generation in quantum dots and nanowires CdSe was previously investigated. However up to now, this issue in CdSe nanoplatelets has not yet been studied. In this work, we have demonstrated and investigated for the first time the second harmonic generation in colloidal solution CdSe nanoplatelets. We have studied a core-shell colloidal solution of atomically flat heterostructures that represent the 3.5 monolayers of CdSe with 3 CdS monolayers shell on each side grown by the colloidal atomic layer deposition. The experimental sample was excited by femtosecond laser pulses with 320 fs duration, 100 kHz repetition rate and a wavelength of 1064 nm. The spectra of the second harmonic radiation were measured depending on the incident laser pulses intensity. The measured dependence was theoretically approximated and the source of the second harmonic generation in nanoplatelets was proposed. We believe that discovery of the SHG in these nanostructures allows to improve both spectral and temporal resolution for their use as biomarkers, for optical imaging and so on.
    11770-33
    Author(s): Alexander M. Smirnov, M. V. Lomonosov Moscow State Univ. (Russian Federation), Kotelnikov Institute of Radio Engineering and Electronics (Russian Federation); Anastasiya D. Golinskaya, Maria V. Kozlova, Bedil M. Saidzhonov, Roman V. Vasiliev, Vladimir N. Mantsevich, Vladimir S. Dneprovskii, M. V. Lomonosov Moscow State Univ. (Russian Federation)
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    Semiconductor nanocrystals have been actively studied due to their unique physical and chemical properties and are actively being implemented in nanophotonics devices. Nanostructures created by the colloidal synthesis with design shape, size and crystal structure are widely used. Recently, colloidal semiconductor quantum wells (nanoplatelets) have been created. Colloidal semiconductor nanoplatelets (NPLs) are atomically flat nanocrystals which demonstrate a zinc blend crystal structure with a [001] axis. Strong quantum confinement of NPLs and high exciton binding energy are provided by anisotropic of nanocrystals with several nanometers thick and tens of nanometers in lateral dimensions which can be used to tune the optical absorption and photoluminescence spectra. In this paper we present the peculiarities of excitation, interaction and relaxation of excitons in colloidal CdSe nanoplates depend on type and thickness of shell in the case of one-photon exciton excitation by laser pulses (λ=540 nm, τ=10 ns). The linear and nonlinear absorption spectra of colloidal CdSe NPLs were studied. The linear absorption spectrum of the NPLs demonstrate three well-resolved absorption bands that correspond to heavy hole, light hole and spin-orbital exciton transitions at room temperatures due to the almost complete absence size dispersion of nanocrystals. The differential transmission spectra allowed us to reveal experimentally the lowest four band structure of CdSe/CdS nanoplatelets at the Γ point of Brillouin zone and its modification with CdS shell thickness changing for the first time. In addition, the features of exciton-exciton interaction, exciton-phonon interaction, as well as the process of energy transfer between light and heavy excitons to exciton relaxation were investigated. The rate equations describing the exciton-exciton and exciton-electron interactions was applied for analyzing the recombination and interaction of excitons in the colloidal NPLs under high excitation densities. This work was partially supported by the Russian Foundation for Basic Research №20-32-70001
    11770-34
    Author(s): Anton Putintsev, Anton V. Zasedatelev, Skolkovo Institute of Science and Technology (Russian Federation); Kirsty McGhee, The Univ. of Sheffield (United Kingdom); Tamsin Cookson, Univ. of Southampton (United Kingdom); Kyriacos Georgiou, The Univ. of Sheffield (United Kingdom); Denis Sannikov, Skolkovo Institute of Science and Technology (Russian Federation); David Lidzey, The Univ. of Sheffield (United Kingdom); Pavlos G. Lagoudakis, Skolkovo Institute of Science and Technology (Russian Federation)
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    Strongly coupled organic microcavities are up-and-coming material systems for ambient polaritonics. A broad range of suitable materials made possible the experimental observation of polariton lasing across the whole visible range, as well as device-concepts ranging from ultra-fast transistors and all-optical logic gates to single-photon switching, all at room temperature under ambient conditions. Unlike the case of inorganic semiconductor microcavities, where continuous-wave excitation allows for the replenishment of particle losses, leading to the realization of steady-state polariton condensates, in organic semiconductors photobleaching and polaron formation prevent CW operation. BODIPY dyes have been the subject of thorough studies for their applications in the strong coupling regime. Strongly coupled BODIPY microcavities and polariton lasing in these structures allow for highly monochromatic tunable coherent emission of duration up to ~two picoseconds. Here, we use a single-mode lambda/2 strongly coupled microcavity of a BODIPY dye molecule, employ a single-shot dispersion imaging technique to study polariton lasing in a planar organic microcavity, and achieve a quasi-steady state exciton-polariton condensation under single-shot excitation in such systems. Temporal dynamics of a single-shot exciton-polariton lasing is of particular interest and importance for understanding rates of depletion and replenishment of the exciton reservoir and polariton states, respectively, under pulsed excitation. Moreover, the direct measurement of the condensate lifetime provides valuable insight into the transient processes of nonequilibrium polariton condensation. Long-lasting condensates exceeding polariton lifetime for several orders of magnitude push the system one step closer towards the regime of dynamic equilibrium and could be a missing puzzle towards polariton applications such as connected polariton devices and condensate lattices implemented at ambient conditions, opening the possibility for all-optical polariton circuitry on a chip.
    Session 6: Applications
    11770-36
    Author(s): Nuno A. Azevedo Silva, Tiago D. Ferreira, Duarte J. Silva, Ariel Guerreiro, INESC TEC (Portugal)
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    All-optical computing is a long-standing goal in optical sciences that promises ultra-fast and energy-efficient computation by leveraging light-speed information transfer and processing of optical data signals. Amongst many proposals, soliton computing stands as an interesting framework that seeks computational solutions based on the particle-like behavior of these self-localized wave solutions which are often used as optical data information carriers. Yet, like many of the efforts in optical computing, the lack of controllability at the experimental level remains the major obstacle to compete with electronic solutions based von Neumann-like architectures. To work around this obstacle, research has recently pushed for the exploration of alternative and neuromorphic-inspired computing frameworks, where reservoir computing appears as one of the most promising ones by enabling a given nonlinear physical system to work as a computing platform. In this work, we explore how the reservoir computing paradigm can be used to implement a versatile and robust soliton-based computing solution by using a discrete soliton chain as a reservoir. Exploring its tunable dynamics, we demonstrate how nonlinear dynamics allows our system to perform accurate regression and classification tasks of non-linear separable datasets. The numerical results presented pave not only a way for the physical realization of novel hardware solutions, but also a path to inspire future research on soliton-based computing on various physical platforms leveraging on its ubiquity across multiple fields of science.
    11770-37
    Author(s): Lennart Hinz, Markus Kästner, Eduard Reithmeier, Leibniz Univ. Hannover (Germany)
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    Benefiting from recent innovations in the smartphone sector, liquid optics in very compact designs have been cost-effectively introduced to the market. Without mechanical actuation, a focus variation can be adjusted within fractions of a second by curving a boundary layer between two liquids by applying a pulse width or amplitude modulated potential. Especially in the field of endoscopy, these innovative optical components open up many application possibilities. Conventional, mechanical zoom lenses are not very common in endoscopy and can only be miniaturized at considerable effort due to the necessary actuation and the complex design. In addition, the mechanical response is slow, which is a particular disadvantage in hand-held operation. A calibrated camera provides a two-dimensional camera pixel translated into a three-dimensional beam and, together with distortion correction enables the extraction of metric information. This approach is widely used in endoscopy, for example, to measure objects in the scene or to estimate the camera position and derive a trajectory accordingly. This is particularly important for triangulation-based 3D reconstruction such as photogrammetry. The use of liquid lenses requires a new data set with an adapted camera calibration for each focus adjustment. In practice, this is not feasible and would result in an extensive calibration effort. This paper therefore examines, on the basis of an experimental setup for automated endoscopic camera calibration, the extent to which certain calibration parameters can be modelled and approximated for each possible focal adjustment, and also investigates the influence of a liquid lens on the quality of the actual calibration.
    11770-38
    Author(s): Robin R. Jones, Univ. of Bath (United Kingdom); Tim Batten, Brian Smith, Renishaw plc (United Kingdom); Alejandro V. Silhanek, Université de Liège (Belgium); Daniel Wolverson, Ventsislav K. Valev, Univ. of Bath (United Kingdom)
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    Despite the ubiquity of Raman spectroscopy, fluorescence, poor signal strength and photobleaching pose a significant challenge to researchers in the biomedical field. Here, we demonstrate a 17-fold signal enhancement in Raman spectra of crystal violet via surface-enhanced Raman scattering (SERS). The SERS substrate was fabricated by electron beam lithography (EBL); the nanostructured surface was an array of G-shaped elements made of Au on SiO2/Si. In addition to the SERS spectra, finite-difference time-domain simulations were performed to illustrate the distribution of electric-field hot-spots on the SERS substrate. The electric-field hot-spots were prominent at the vertices and edges of the nanostructured G-shaped motifs. The results presented here demonstrate that EBL is a high-end choice for SERS substrate fabrication that opens the way for more complex Raman spectroscopies, for instance involving nonlinear optics or chiral analytes.
    11770-39
    Author(s): Anastasiia Vasylchenkova, Univ. College London (United Kingdom); Dmytro Salnikov, Dmytro Karaman, Oleg Vasylchenkov, Kharkiv Polytechnic Institute (Ukraine); Yaroslav E. Prylepskiy, Aston Univ. (United Kingdom)
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    The Nonlinear Fourier Transform (NFT) signal processing has attracted considerable attention as a promising tool for the fibre nonlinearity mitigation in optical communications: the approach allows effective linearisation of the nonlinear optical-fibre channel and reach higher communication system’s capacity. However, the considerable mathematical complexity of the NFT-based processing algorithms and their distinction from “conventional” methods require our investing additional efforts to adapt this approach for practical applications. In our work, we demonstrate a hardware implementation of the fast direct NFT operation, which is realised at the receiver to map the optical signal to its nonlinear Fourier spectrum (i.e. to demodulate the data). The main component of the algorithm is the matrix-multiplier unit, implemented on field-programmable gate arrays (FPGA) and used for the estimate of required hardware resources. To design the best performing implementation in limited resources, we perform accuracy analysis to get an optimal bit width. The fast NFT algorithm that we analyse, is based on the FFT, which leads to the O(N log2N) overall method's complexity for the signal consisting of N samples. Our analysis revealed the significant demand in DSP blocks on the used board, which is caused by complex numbers, matrix operations, and FFTs. Nevertheless, it seems to be possible to involve parallelisation and build the hardware performing the NFT operation, which should bring about the possibility to process the optical signal with NFT methods on-line.
    11770-40
    Author(s): Sahar Wehbi, ALPhANOV (France); Tigran Mansuryan, Raphael Jauberteau, Alessandro Tonello, Xlim (France); Katarzyna Krupa, Institute of Physical Chemistry, Polish Academy of Sciences (Poland); Stefan Wabnitz, DIET, Sapienza University of Rome Via Eudossiana 18 (Italy), CNR-INO, Istituto Nazionale di Ottica (Italy); Hideaki Kano, Department of Applied Physics, Graduate School of Pure and Applied Sciences, University of Tsukuba (Japan), Institute of Applied Physics, University of Tsukuba (Japan), Department of Chemistry, Kyushu University (Japan); Philippe Leproux, Xlim (France); Sebastien Vergnole, ALPhANOV (France); Vincent Couderc, Xlim (France)
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    In this study, we report on experiments of spatio-temporal nonlinear frequency conversion in a periodically poled Lithium Niobate (PPLN) crystal designed for second-harmonic generation (SHG). We demonstrated a novel supercontinuum source based on the mixing of second and third-order nonlinearities. We could adjust the (X(2), X(3)) nonlinearities by controlling the input laser polarization orientation, the pulse duration and the PPLN crystal temperature. We obtained an ultra-broadband spectrum, ranging from visible to infrared domains, by pumping a 20-mm-long PPLN crystal with a 3 ps pulse at 1030 nm. This broadband pulse was used to achieve direct multiplex Coherent Anti-Stokes Raman Scattering (M-CARS) imaging, without the need for any optical delay line to temporally synchronize the pump and the Stokes waves. Simultaneous vibrational signatures ranging from -3200 cm-1 to -500 cm-1 were obtained. Several filters were placed on the broadband supercontinuum path, to shape the output spectrum between 1030 nm and 1650 nm, before sending it into the microscope. The output spectral analysis allows for the demonstration of multimodal imaging, by using SHG, M-CARS and multiphoton fluorescence processes.
    11770-41
    Author(s): Tiago D. Ferreira, Univ. do Porto (Portugal), INESC-TEC (Portugal); João Novo, Orfeu Bertolami, Univ. do Porto (Portugal), Centro de Física do Porto (Portugal); Nuno A. Silva, Univ. do Porto (Portugal), INESC TEC (Portugal); Ariel Guerreiro, Univ. do Porto (Portugal), INESC-TEC (Portugal)
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    The Theory of General Relativity is currently the most accepted model to describe gravity, and although many experiments and observations continue to validate it, recent astrophysical and cosmological observations require to include new forms of matter and energy (dark matter and dark energy), to be consistent. Modified theories of gravity with non-minimal coupling between curvature and matter are extensions of the Theory of General Relativity and have been proposed to address these shortcomings. Interestingly, matter at large scales behaves as a fluid and under certain approximations, the field equations can be approximated to a generalized Schrödinger-Newton system of equations. This model is largely found in the nonlinear optical systems, in particular, to describe light propagating in nonlinear and nonlocal optical materials and also as a base model for the development of many optical analogues. Due to this, there are a wide variety of numerical methods developed to tackle this type of mathematical models, and that can be used to study these alternative gravity models. In this work, we explore the application of these numerical techniques based on GPGPU supercomputing, initially developed to study light propagating in nonlinear optical systems, to explore a particular non-minimal coupled gravity model. This model, in the nonrelativistic limit, modifies the hydrodynamic equations with the introduction of an attractive Yukawa potential and a repulsive one proportional to the matter density. We used the Schrödinger-Newton formalism to numerically study this model and, through the imaginary-time propagation method, we found stationary solutions that were sustained by the repulsive potential introduced by the non-minimal coupled model, even in the absence of a pressure term. We developed an analytical study in the Thomas-Fermi approximation and compared the predictions with numerical solutions. Finally, we explored how this gravity model may be emulated in the laboratory as an optical analogue.
    11770-42
    Author(s): Tímea Grósz, Máté Kurucz, Roland Flender, Ádám Börzsönyi, ELI-ALPS (Hungary); Ugnius Gimzevskis, Arturas Samalius, OPTOMAN (Lithuania); Dominik Hoff, Single Cycle Instruments (Germany); Bálint Kiss, ELI-ALPS (Hungary)
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    One of the most widespread and reliable techniques for spectral phase characterization of optical elements is spectrally resolved interferometry (SRI), which utilizes a two-arm interferometer illuminated by a broadband light source and a spectrometer to record the generated spectral fringes, which are usually evaluated by using Fourier-transform-based methods. One detriment to these methods, that they require high spectral resolution. Considering that most of the spectrometers in the mid-infrared (MIR) region have typically a few nm spectral resolution, we propose two alternative methods for measurements in this spectral region, second harmonic assisted SRI (SH-SRI) and dual-band SRI. The SH-SRI method utilizes second harmonic generation, which allows for high-precision phase retrieval by shifting the detection range from the MIR regime to the near-infrared, where high-resolution spectrometers are commercially available. The dual-band SRI method has the capabilities of the SH-SRI, while simultaneously probing the optical element at the second harmonic frequency band as well. Using the Fourier transform method, the acquired phase can be obtained from a single interferogram at both frequency bands simultaneously, which effectively doubles the measurement bandwidth compared to the original SRI and the SH-SRI without increasing the requirements on the bandwidth and the resolution of the spectrometer. To determine the performance of these new schemes, we have measured the spectral phase shift of several optical windows with both SH-SRI and dual-band SRI. Their accuracy was significantly higher than that of the conventional SRI technique that relied on low-resolution spectrometers operating in the MIR region. We used the SH-SRI technique also to verify the phase performance of custom-made MIR dispersive mirrors, designed with specific dispersion characteristics. With the dispersive mirrors, we were able to compress our spectrally broadened pulses to 19.6 fs (<2 cycles) at 3170 nm central wavelength with 8.2 W average power.
    11770-45
    Author(s): Nikita Tarasov, Aston Univ. (United Kingdom); Leonid A. Melnikov, Yuri Gagarin State Technical Univ. of Saratov (Russian Federation); Ilya D. Vatnik, Novosibirsk State Univ. (Russian Federation); Yulia A. Mazhirina, Saratov State Technical Univ. (Russian Federation); Dmitry V. Churkin, Novosibirsk State Univ. (Russian Federation)
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    Random lasers are the type of lasers where feedback is provided by the randomly distributed inhomoginities within the media. Since the first demonstration of the random fiber laser based on Rayleigh backscattering in optical fibers the field has undergone extensive development. In the present work we experimentally develop a self-gain-switched random fiber laser operating via Raman gain with a possibility of self-adjustement of repetition rate depending on the power. The random fiber laser generation is achieved in an anomalous dispersion fiber near 1550 nm. We used different fiber length L ranging from 27 to 75 km. The dynamics of the output generation well above the threshold demonstrates multiscale behavior. There are stochastic pulses of <200 ps duration. At the same time, slowly varying envelope clearly demonstrates pulsating behavior with typical pulse duration of hundreds of microseconds (for example, the repletion rate is close to 3.3 kHz for 48 km fiber). The repletion rate is stable over substantial pump power range (in the range of 2.4-5.2 W of pump power for 48 km fiber). Surprisingly, further increase of pump power leads to step-like increase of the repetition rate to 5.5 kHz. We clarify in our experiments, that repetition rate should satisfy the relation (2k+1)*c/(4Ln), where k is an integer number, n is refractive index, and c is a speed of light. Note that the repetition rate is different from the repetition rate of a laser with a conventional (not random) cavity where it is defined by roundtrip time of the cavity. The demonstrated switchable regime has a low timing jitter and could be promising for reconfigurable high average power applications. We clarify that the reason for observed pulsed behavior is counter propagating Stokes wave competition with a well pronounced agreement between experimental data and performed numerical modelling.
    Session PS: Poster Session
    11770-51
    Author(s): Watheq Al-Basheer, King Fahd Univ. of Petroleum & Minerals (Saudi Arabia)
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    In this paper, the ultraviolet output of frequency-doubled OPO laser at 266 nm was employed to obtain highly-resolved (2+1) resonance-enhanced multiphoton ionization (REMPI) and mass spectra of supersonically-expanded and jet-cooled molecular pulses of iodomethane. The molecular sample consisted of a 3% neat iodomethane gas dissolved in helium. The REMPI and mass spectra of iodomethane were obtained using a two-meter time-of-flight (TOF) mass spectrometer coupled with a microchannel plate detector that was kept at 4K volts. The laser power density effect on the (2+1) REMPI process was also investigated by focusing and defocusing the laser pulses using 30 cm and 75 cm biconvex lenses, respectively. By monitoring I+ and CH3+ fragments, it was evident that 3 photons were involved in the REMPI process.
    11770-53
    Author(s): Vasily V. Spirin, Jose L. Bueno-Escopedo, C. A. Lopez-Mercado, Ctr. de Investigación Científica y de Educación Superior de Ensenada B.C. (Mexico); Patrice Mégret, Univ. de Mons (Belgium); Dmitry A. Korobko, Igor O. Zolotovskii, Ulyanovsk State Univ. (Russian Federation); Andrei A. Fotiadi, Univ. de Mons (Belgium), Ulyanovsk State Univ. (Russian Federation), Ioffe Institute (Russian Federation)
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    Linewidth narrowing and stabilization of semiconductor laser light generation is of great research interest governed by the huge demand of compact cost-effective narrow-band laser sources for many potential applications. In 2012 we have demonstrated a simple kHz-linewidth laser just splicing a standard distributed feedback (DFB) laser diode and a few passive telecommunication components. The principle of operation employs the mechanism of self-injection locking that significantly improves DFB laser performance. While a typical linewidth of free-running DFB semiconductor lasers ranges from a few to tens MHz, self-injection locking of a DFB laser through an external fiber ring cavity causes a drastic reduction of its laser linewidth down to a few kHz. The advantage of the proposed configuration is that the same external fiber ring cavity could be used for self-injection locking of a DFB laser and as Brillouin scattering media to generate Stokes shifted optical wave. However, a continuous laser operation at two frequencies has not been reported yet preventing it from many prosperous photonic applications. Here, we introduce a simple dual-frequency laser configuration. In our approach, the implementation of self-injection locking into the Brillouin ring fiber laser helps to maintain coupling between the DFB laser and an external high-Q fiber cavity enabling dual-frequency laser operation. Specifically, the same ring fiber cavity is used to generate narrow-band light at the pump frequency (through self-injection locking mechanism) and narrow-band laser light at Stokes frequency (through stimulated Brillouin scattering). The system is supplied by a low-bandwidth active optoelectronic feedback circuit controlled by a low-cost USB-DAQ card that helps the laser to maintain the desired operation mode. The fiber configuration reduces the natural Lorentzian linewidth of light emitted by the laser at pump and Stokes frequencies down to 270 Hz and 220 Hz, respectively, and features a stable 300-Hz-width RF spectrum recorded with the beating of two laser outputs. We have explored key features of the laser performance, revealing its stability and applicability to RF harmonic generation of high spectral purity as an additional benefit of the proposed technique.
    11770-54
    Author(s): Dmitry A. Korobko, Igor O. Zolotovskii, Sergey G. Moiseev, Ulyanovsk State Univ. (Russian Federation); Andrei A. Fotiadi, Ulyanovsk State Univ. (Russian Federation), Univ. de Mons (Belgium)
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    Surface plasmon–polaritons (SPPs), propagating bound oscillations of electrons and light at a metal surface, exhibit the capacity for subwavelength field confinement and enhancement that make them a promising photonic platform at the nanometer scale. In this work we report the results of theoretical investigations of SPP propagation in metal film with varying thickness lying on a dielectric substrate. It is shown that the SPP propagation can be described by an equation of the type of the nonlinear Schrödinger equation. The main parameters of the nonlinear Schrödinger equation for the SPP − Kerr nonlinearity and dispersion coefficients− are derived from the basic SPP dispersion relation. The dependences of these coefficients on the film thickness are obtained. It is shown that the high-frequency SPP dispersive branch satisfies the conditions of the development of modulation instability. According to estimates, the magnitude of the modulation gain is sufficient to generate ultrashort pulse train from the initial modulated SPP wave on the propagation length of about 100 nm. The peculiar features of modulated SPP propagation in the metal film with varying thickness are studied. Analogies between the light wave propagation in a nonlinear dispersion decreasing fiber and SPP propagation in the metal film with increasing thickness are shown. Numerical simulations performed confirm the theoretically predicted generation of ultrashort pulse trains with THz an sub-THz repetition rates from an initially modulated SPP wave in a film with a longitudinally increasing thickness on propagation length of about 100-200 nm.
    11770-55
    Author(s): Cesar Lopez-Mercado, Jose L. Bueno-Escopedo, M. C. Maya-Sanchez, Sergei Miridovov, Ctr. de Investigación Científica y de Educación Superior de Ensenada B.C. (Mexico); Dmitry A. Korobko, Igor O. Zolotovskii, Ulyanovsk State Univ. (Russian Federation); Vasily V. Spirin, Ctr. de Investigación Científica y de Educación Superior de Ensenada B.C. (Mexico); Andrei A. Fotiadi, Univ. de Mons (Belgium), Ulyanovsk State Univ. (Russian Federation), Ioffe Institute (Russian Federation)
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    Low-noise lasers are a powerful tool in precision spectroscopy, displacement measurements, and the development of advanced optical atomic clocks. All applications benefit from lower frequency noise and robust design, however, the generation of microwave signals additionally requires narrowband lasing at two frequencies. Here, we introduce a simple optoelectronic oscillator enabling the generation of a stable ultra-narrow microwave carrier signal with low phase noise based on stimulated Brillouin scattering. A cost-effective sub-kilohertz Brillouin fiber ring laser with stabilized self-injection locked pump DFB (Distributed Feedback Laser) laser is used for this purpose. The system is supplied by a low-bandwidth active optoelectronic feedback controlled by a low-cost USB-DAQ card. The full-width of generated microwave signal at -3 dB level is approximately equal to 300 Hz with a peak maximum at ~10.946 GHz. The strongest parasitic harmonics shifted from carrier signal peak by ±50 kHz, ±450 kHz, and ±900 kHz are below the main peak by 45-50 dB. A phase noise below −90 dBc/Hz for a frequency offset above 10 kHz from the carrier after passing the 20 km length test fiber has been achieved.
    11770-56
    Author(s): Dmitry A. Korobko, Dmitry A. Stoliarov, Pavel Itrin, Valerya Ribenek, Ulyanovsk State Univ. (Russian Federation); Andrei A. Fotiadi, Ulyanovsk State Univ. (Russian Federation), Univ. de Mons (Belgium); Regina V. Gumenyuk, Ulyanovsk State Univ. (Russian Federation), Tampere Univ. of Technology (Finland)
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    Soliton fiber lasers with passive harmonic mode-locking (HML) have been known for several decades as reliable sources of pulse trains with a high repetition rate. They are commonly employed as frequency comb generators in a wide list of applications in spectroscopy, telecommunications, microwave photonics. Besides that exhibiting advantageous consumer properties, such as compactness, reliability, low cost and convenience of beam delivery approach these sources are among the most attractive alternatives for material processing, medicine lasers and other areas. In the first group of these lasers the HML occurs due to special intra-cavity periodic filter with a free spectral range (FSR) which is a multiple of the main cavity FSR and equals to the pulse repetition rate. The second group of HML lasers in this classification is attractive for the scientific community due to the automatic arrangement of strongly periodic pulse pattern in the laser cavity through pulse repulsion. However, it is difficult to specify the mechanism of pulse repulsion for each case. It can be based on interaction through saturating and relaxing dissipative parameters, continuous-wave (CW) radiation component, dispersion waves, or acoustic waves induced by electrostriction, etc. A common feature of all interaction induced effects is low intensity, in many cases only slightly exceeding the noise level. The noise-induced fluctuations in the time interval of the HML pulse train are known as HML timing jitter, and its value is significantly higher than the timing jitter in lasers operating at fundamental frequency. It is a major drawback of the HML laser technology. We report the stabilizing frequency shift effect in harmonic mode-locking ring soliton fiber laser that is studied theoretically and numerically. We demonstrate that the frequency shift contributes to an increase in the hardness of interpulse interactions and can led to stabilization of the periodic arrangement of pulses. The experiment carried out confirms the theoretical predictions and the results of numerical simulation.
    11770-57
    Author(s): Evgenii Viktorov, Saint Petersburg State Univ. (Russian Federation); Kaspars Miculis, Moscow Engineering Physics Institute (Russian Federation); Alexander Pastor, Pavel Serdobintsev, Saint Petersburg State Univ. (Russian Federation); Nikolai Bezuglov, Saint Petersburg State Univ. (Russian Federation), Rzhanov Institute of Semiconductor Physics (Russian Federation), Univ. of Latvia (Russian Federation)
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    Optical diagnostics of gas media can be essentially improved due to analyzing fluorescence signals of exited polarized atoms. External magnetic fields, for instance, result in diverse types of oscillating structures in detected signals. This allows, firstly, to carry out accurate measurements of the state parameters of atoms beyond the Doppler broadening, and secondly, to create and implement sensitive magnetometers. Traditional methods of spectroscopy are mainly associated with bound-bound optical transitions. This work is focused both experimentally and theoretically on the possibility of studying the photocurrent oscillations during photoionization of argon and xenon atoms in a supersonic beam. We used a “pump-probe” experiment with a three-photon excitation scheme for the Ar atomic state and a two-photon excitation scheme for the Xe atomic state. Subsequent single-photon ionization by probe right-polarized photons takes place with the delay time t and occurs in the presence of a magnetic field. The temporal dependence I(t) of the photoelectron signal exhibits oscillations on the first two Larmor frequency overtones. The obtained theoretical curve of the electron-yield intensity provides the proper approximation of the experimental data. The photoelectron-yield intensity I(t) is derived on the base of the irreducible tensors operators technique for atomic and photon polarization moments, along with the sum rules. The aggregated intensity of photocurrent I(t) is consists of the contributions from bound-free optical transitions both with increasing and with decreasing the orbital moment. The ratio of statistical weights for these outgoing channels means that the transitions with increasing the photoelectron orbital moment play a dominant role. That result is in an agreement with the Bethe rule.
    11770-58
    Author(s): Yiling Song, Weiwei Liu, Peixiang Lu, Huazhong Univ. of Science and Technology (China)
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    2D organic–inorganic hybrid perovskites are promising materials for next-generation optoelectronic devices. Nevertheless, 2D perovskites still suffer from performance-limiting trap states and possess fundamental photophysical effects that remain poorly understood. Herein, a photoinduced trap passivation for enhanced photoluminescence (PL) in 2D hybrid perovskites is reported. Under two-photon excitation, the PL emission of the 2D hybrid perovskites exhibits a gradual increase in intensity and lifetime, due to the photoinduced trap passivation by interacting with oxygen in ambient environment. Interestingly, the PL increase shows distinct features at the surface and in the bulk of the 2D perovskites, which can be well revealed by a photoinduced oxygen-diffused trap passivation model. Moreover, the PL increase and relaxation can recycle for several times, which suggests an excellent repeatability of the photoinduced trap passivation. The photoinduced trap passivation is critical for fundamental study of light–matter interaction in 2D perovskites, and shows great promise for improving the optoelectronic responses for functional devices.
    11770-59
    Author(s): Sergey Krasikov, Alexander Chukhrov, Alexey Yulin, Andrey Bogdanov, ITMO Univ. (Russian Federation)
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    Bound states in the continuum are non-radiating solutions of the wave equation which are completely decoupled from the radiation continuum and therefore it is impossible to excite them from the far-field in linear systems. In this work, we develop a general theory of parametric excitation of BICs in nonlinear systems via spontaneous symmetry breaking, which results in a coupling between BIC and bright modes of the system. Using the temporal coupled-mode theory and perturbation analysis, we found the threshold intensity for excitation of BIC and study the possible stable solutions depending on the pump intensity and frequency detuning between the pump and BIC. We revealed that at some parameters of the pump beam, both BIC and the bright mode can have non-zero amplitudes forming a stable hybrid state. Also, at some parameters, there are no stable solutions and BIC can be used for frequency comb generation. Our findings can be very promising for use in nonlinear photonic devices and all-optical networks.
    11770-60
    Author(s): Patrice Salzenstein, Ekaterina Pavlyuchenko, Institut Franche-Comte Electronique Mecanique Thermique et Optique (France)
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    We propose in this paper to come back to the starting conditions of optoelectronic oscillators and in particular with regard to the Barkhausen conditions. The context is first of all the anniversary of the hundred years since the discovery of oscillations conditions and their optimization by Heinrich Barkhausen, whose principles we recall. We then give through the study of an example, how these conditions are relevant to optimize the start of the oscillation. The type of optoelectronic oscillator chosen for this study is an optoelectronic oscillator based on optical delay lines. The optical signal carrier wavelength is 1.55 µm, the typical oscillation frequency is 10 GHz. It is all the more interesting to approach this subject in the context of the centenary of this discovery, which we can see how the advances made possible by H. Barkhausen are relevant and still relevant today.
    11770-61
    Author(s): Ekaterina Pavlyuchenko, Patrice Salzenstein, Institut Franche-Comte Electronique Mecanique Thermique et Optique (France)
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    The Brillouin Light Scattering characterization method allows us to better understand the properties of materials. This method consists in sending a high power laser signal focused on an area of the material to be characterized. The light-matter interaction in the material induces a phononic wave which moves at a certain speed that we will be able to estimate by analyzing a laser signal re-emitted by the material. This signal is shifted by a microwave frequency characteristic of the speed of propagation of the phonononic waves in the material. The microwave frequencies involved and which can be detected are typically of the order of 3 to 150 GHz. We propose in this paper to continue our investigations to have a more precise idea of the uncertainty which one can give on a result of frequency shift corresponding to the determination of a speed of propagation of phononic waves through or on the surface of the material to be characterized.
    11770-62
    Author(s): Edgar Ferreira, Jesus Eduardo Castellanos-Águila, Univ. de Guanajuato (Mexico); Alejandro Vazquez, Univ. Autónoma de Nuevo León (Mexico); Mónica Trejo-Durán, Univ. de Guanajuato (Mexico)
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    In the present work we show the results of theorical calculations of nonlinear optical properties of choline chloride – urea deep eutectic solvent mixture. Deep eutectic solvents are a novel kind of solvents with similar properties of classic ionic liquids but with advantages like been easy to prepare and biodegradable. We had obtained the most stable structure using DFT optimization with M06-2X/6-311G(d,p). Then their static and dynamic (at 477 nm) first and second order hyperpolarizabilities were obtained. These results were used to estimate the third order nonlinear susceptibility showing that this solvent is promising for nonlinear optics related application.
    11770-63
    Author(s): Tiago D. Ferreira, Univ. do Porto (Portugal), INESC TEC (Portugal); Nuno A. Silva, Ariel Guerreiro, Univ. do Porto (Portugal), INESC TEC (Portugal)
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    The last years saw the emergence of nonlinear optical materials, with local and nonlocal nonlinearities, as experimentally accessible systems to implement optical analogues of quantum fluids. In these systems, a light beam propagating in the nonlinear medium can be interpreted as a fluid, where the diffraction in the transverse plane to the propagation gives the effective mass of the fluid and the medium nonlinearity mediates the required interactions between the photons. This fluid interpretation and its application have been extensively studied, from the creation of superfluid-like flows and the study of phenomena associated with this effect to the implementation of gravity analogues. Furthermore, many optical materials have been considered, with a special interest in the ones that offer tunable mechanisms that allow to easily control the system properties to better explore and emulate the different phenomena. Recently, nematic liquid crystals have been proposed as an interesting tunable material capable of supporting superfluids of light. These systems have a nonlocal character and offer external mechanisms that can be used to tailor the nonlinearity to better emulate the desired analogue system. Indeed, through the application of an external electric field perpendicular to the direction of propagation, is it possible to control the nonlocal length of the nonlinearity. This mechanism offers interesting opportunities in the present context. In this work, through numerical methods based on GPGPU supercomputing, we explore the possibility of observing superfluid effects in defocusing nematic liquid crystals. In particular, we explore the possibility of observing the drag force cancelation and the emission of quantized vortices, which are two manifestations of a superfluid flow. Furthermore, we also discuss the possibility of using these systems for creating an analogue of quantum turbulence with these materials. These studies constitute a stepping-stone towards the implementation of gravity analogues with nematic liquid crystals.
    11770-64
    Author(s): Nuno A. Azevedo Silva, Tiago D. Ferreira, Vicente Rocha, Ariel Guerreiro, INESC TEC (Portugal)
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    Fluids of light refer to a research line that makes use of fluid-like properties of light to establish experimentally controllable physical analogues of quantum fluids. In short, the analogy is grounded on a formal equivalence between the (i)mean-field theory for quantum fluids and (ii)the hydrodynamic interpretation of the electromagnetic field, turning the dynamics of an optical beam into an analogue quantum system with interparticle interactions mediated by the nonlinear optical response of the media. In this work, we will use the concept to explore the quantum turbulence regime by generating and probing turbulent phenomena on an optical beam propagating in a defocusing nonlinear media. We propose an analogue two-component quantum fluid by making use of orthogonal polarizations and incoherent beam interaction, obtaining a system for which the perturbative excitations follow a modified Bogoliubov-like dispersion relation. We show that the dispersion relation features regions of instability that can be used to excite turbulent phenomena and that are easily tuned by manipulating the relative angle of incidence between the two components, allowing to define an effective range of energy injection into the system. Our numerical results support the predictions and show evidence of direct and inverse turbulent cascades expected from weak wave turbulence theories. Finally, we also provide a discussion on a possible experimental realization and how it allows access to quantum turbulence in regimes well beyond the state of the art using the controllable aspects of tabletop experiments with fluids of light.
    11770-65
    Author(s): Mikhail Sergeyevich Savelyev, National Research Univ. of Electronic Technology (Russian Federation), I.M. Sechenov First Moscow State Medical Univ. (Russian Federation); Pavel N. Vasilevsky, National Research Univ. of Electronic Technology (Russian Federation); Alexander Gerasimenko, National Research Univ. of Electronic Technology (Russian Federation), I.M. Sechenov First Moscow State Medical Univ. (Russian Federation); Alexander Yu Tolbin, Institute of Physiologically Active Substances (Russian Federation)
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    In this study, J-type dimeric copper phthalocyanine in dimethylformamide (DMF) was investigated to show strong nonlinear absorption due to the reverse saturable absorption (RSA) under single nanosecond pulses (16 ns at a wavelength of 532 nm), which significantly exceeds the lifetimes of excited states. In the case of a femtosecond laser, the effect of spatial self-phase modulation was observed, with no contribution from nonlinear absorption being found. The only linear absorption was detected under pulses of 140 fs at a wavelength of 790 nm. The femtosecond pulse repetition rate was 80 MHz which corresponds to a delay between single pulses of about 12.5 ns. Both analytical wavelengths used were outside the intense absorption region (Q- and B- bands) of J-type dimeric copper phthalocyanine in the UV/Vis/NIR spectrum. In the case of femtosecond laser radiation, a sufficient population of excited states was not achieved due to the low peak fluence (~ 0.03 mJ/cm2). For the single nanosecond pulses, the threshold fluence density was ca. 30 mJ/cm2. In the switch circuit, such material should be placed horizontally to exclude asymmetric thermal convection resulting from the gravity effect.
    11770-66
    Author(s): Arturs Bundulis, Institute of Solid State Physics, Univ. of Latvia (Latvia); Martins Rutkis, Institute of Solid State Physics (Latvia)
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    We demonstrated a new approach to measuring third-order nonlinear optical effects using an experimental setup incorporating both Z-scan and Mach-Zehnder interferometer methods. This method could be especially purposive for thermo-optical effect studies as it can simultaneously probe thermal gradient profile as well as absolute temperature changes induced by an optical beam. The experimental setup was tested using chloroform. Experimental measurements were carried out using 1064 nm Nd:YAG laser with 8 ns pulse width and 40 kHz pulse repetition rate. The measured nonlinear refractive index of chloroform was mainly induced by the thermo-optical effect. As thermo-optical response depends on beam size at focal length, measurements were carried out with 35 mm and 125 mm focal length lenses. Measured nonlinear refractive index values of Z-scan and interferometric measurements gave the same value indicating that this method can be used for thermo-optical effect studies.
    Conference Chair
    Univ. degli Studi di Roma La Sapienza (Italy)
    Conference Chair
    King's College London (United Kingdom)
    Conference Chair
    Alexei M. Zheltikov
    Lomonosov Moscow State Univ. (Russian Federation)
    Program Committee
    Centro de Fisica de Materiales (Spain)
    Program Committee
    Univ. of Tsukuba (Japan)
    Program Committee
    Institut Fresnel (France)
    Program Committee
    Bruno Crosignani
    Caltech (Italy)
    Program Committee
    Reinhard Kienberger
    Max-Planck-Institut für Quantenoptik (Germany)
    Program Committee
    The Australian National Univ. (Australia)
    Program Committee
    Palacky Univ. (Czech Republic)