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This conference covers ultrafast phenomena in bulk semiconductors, semiconducting and metallic nanostructures and devices with emphasis on ultrafast optical and/or coherent phenomena. Manuscripts are solicited in the following topics but not restricted to:

Ultrafast dynamics in semiconductors and heterostructures Coherent dynamics of optical excitations Non-linear optical effects Non-equilibrium carrier transport Ultrafast phenomena carbon nanomaterials Ultrafast phenomena in monolayer semiconductors Spin dynamics and spin manipulation Ultrafast plasmonics THz spectroscopy Ultrafast processes in devices and lasers Ultrafast nano-optics Ultrafast optical properties of metamaterials Ultrafast quantum electronics Ultrafast photocurrents

All contributed papers of conference OE105 given by a young scientist (PhD student or postdoc within the first two years after graduation) are eligible for the award. Note that this award is for contributed papers only. Invited papers and contributions to other symposia do not qualify. To facilitate handing out the award during the meeting, applications will be collected prior to the meeting. To qualify for the award, applicants must:
  • be a young scientist (PhD student or postdoc within the first two years after graduation)
  • be listed as a contributing author (not invited) on an accepted paper within conference OE105
  • have conducted the majority of the work to be presented
  • submit your manuscript online by 29 December 2021
  • present your paper as scheduled
  • be present at the Awards Ceremony.
To Apply, qualified applicants must submit:
  • slides of presentation (Powerpoint or PDF document)
  • additional information about the scientific content of the presentation
  • date of graduation if you have already completed your PhD.
The presentation and the supplementary material should be sent via email to Prof. Markus Betz (please include your SPIE paper number) by 3 January 2022.
In progress – view active session
Conference 11999

Ultrafast Phenomena and Nanophotonics XXVI

In person: 23 - 25 January 2022
View Session ∨
  • 1: Plasmonics
  • 2: Polaritons and Microcavities
  • OPTO Plenary Session
  • 3: Ultrafast Magnetism
  • 4: Quantum Emitters
  • 5: Carrier Dynamics in Semiconductors and 2D Materials
  • 6: Ultrafast Structural Dynamics
  • 7: Nonlinear Optics
  • 8: Ultrafast Aspects of Optical Sources
  • 9: 2D Materials


  • Submissions are accepted through 06-December
  • Notification of acceptance by 20-December

View Call for Papers PDF Flyer
Session 1: Plasmonics
Session Chair: Markus Betz, Technische Univ. Dortmund (Germany)
Author(s): Yonatan Sivan, Ben-Gurion Univ. of the Negev (Israel)
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We review recent progress in modelling and experiments of the femtosecond dynamics of the non-equilibrium energy distribution of electrons in metals following a femtosecond pulse. In particular, we describe an improved modelling approach, and correlated measurements of the spatio-temporal dynamics of the metal permittivity; we also identify the different signature that this dynamics has on the contribution of interband and intraband transitions on the dynamics of the metal permittivity. We then study the effect of chirp on these properties, and discuss insights from photon and electron emission experiments.
Author(s): Andrea Schirato, Margherita Maiuri, Politecnico di Milano (Italy); Remo Proietti Zaccaria, Istituto Italiano di Tecnologia (Italy); Alessandro Alabastri, Rice Univ. (United States); Giulio N. Cerullo, Giuseppe Della Valle, Politecnico di Milano (Italy)
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The spatio-temporal dynamics of hot electrons generated in plasmonic nanostructures via resonant excitation with fs-laser pulses is tailored to induce a transient symmetry breaking of the optical properties at the nanoscale. This effect can be exploited to achieve all-optical control of light with unprecedented speed, including ultrafast transient dichroism from plasmonic metasurfaces with nanocross metaatoms, and ultrafast reconfiguration of diffraction orders in plasmonic metagratings.
Author(s): Aakash A. Sahai, Univ. of Colorado at Denver (United States)
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Plasmonics has been revolutionized by techniques that nano-couple light to optically excite modes in nanomaterials although it was originally discovered using particle beams. Our work relies on particle-beam driven plasmonics to open up the novel possibility of accessing unprecedented tens of TeraVolts per meter EM fields. Electron bunches compressed to densities approaching that of the free electron gas in conducting materials can excite a non-TM and strongly electrostatic surface crunch-in plasmon that sustains tens of TV/m fields. This paper describes a technique to nano-focus particle beams using the surface crunch-in plasmonic mode excited in tapered nanomaterial tubes. Nano-focusing not only increases the density and fields of the bunch as the inverse square of its spot-size but also allows efficient coupling at the nano-scale. Nano-focusing can thus make ultra-dense nanometric particle beams accessible to extend the reach of particle accelerators and advance TV/m plasmonics.
Author(s): Naoki Ichiji, Univ. of Tsukuba (Japan); Murat Yessenov, Kenneth L. Schepler, Ayman F. Abouraddy, CREOL, The College of Optics and Photonics, Univ. of Central Florida (United States); Atsushi Kubo, Univ. of Tsukuba (Japan)
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We investigate space-time surface plasmon polariton wave packet (ST-SPP WP), a conceptual correspondence of a surface-wave to the space-time wave packet (ST WP) that excited on a metal surface through a light-SPP coupling on a nano-scaled ridge. In a framework of the finite-difference time-domain (FDTD) method, a pulsed excitation light was constructed by using hundreds of plane waves of which the lateral and the longitudinal wavenumbers and the frequency were determined according to the dispersion relation of SPP on the metal. The ST-SPP WP launched from the nano-ridge exhibited a significant dispersion-free propagation and a tunability of the group velocity.
Author(s): Eduardo J. C. Dias, Renwen Yu, F. Javier García de Abajo, ICFO - Institut de Ciències Fotòniques (Spain)
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In this work, we take advantage of the strong temperature modulation of the graphene conductivity to propose an all-optical technique of excitation and manipulation of plasmons in graphene and thin metallic films, via the spatial patterning of the temperature of electrons in a graphene film, which can diffract a probe beam and directly excite plasmons. Additionally, we demonstrate the ability of graphene, thin metals films, and graphene-metal hybrid systems to undergo photothermal optical modulation with depth as large as >70% over a wide spectral range extending from the visible to the terahertz spectral domains. We envision the use of ultrafast pump laser pulses to raise the electron temperature of graphene during a picosecond timescale in which its mid-infrared plasmon resonances undergo dramatic shifts and broadenings, while visible and near-infrared plasmons in neighbouring metal films are severely attenuated by the presence of hot graphene electrons.
Session 2: Polaritons and Microcavities
Session Chair: Yonatan Sivan, Ben-Gurion Univ. of the Negev (Israel)
Author(s): Jacob B. Khurgin, Johns Hopkins Univ. (United States); Francesco Monticone, Cornell Univ. (United States); Uriel Levy, The Hebrew Univ. of Jerusalem (Israel)
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Non-Hermitian systems, and in particular exceptional points in them, have attracted significant following within photonics community with a number of “exceptional properties” portending future applications. E Here, we offer a new perspective on the operating principle of these devices, and we theoretically and experimentally show that linear asymmetric mode switching and omni-polarizer action can be easily realized – with the same performance and limitations – using simple configurations that emulate the physics involved in encircling EP’s without the complexity of actual encirclement schemes. The proposed concept of “encirclement emulators” and our theoretical and experimental results may allow a better assessment of the limitations, practical potential, and applications of EP encirclements in non-Hermitian photonics.
Author(s): Kangwei Xia, Thomas Kornher, Univ. Stuttgart (Germany); Zsolt Kis, Laszlo Kovacs, Wigner Research Ctr. for Physics (Hungary); Roman L. Kolesov, Jörg Wrachtrup, Univ. Stuttgart (Germany)
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We present a new strategy to direct quantum functionalization of the LNOI. We incorporate single rare-earth ions in LNOI. Based on spectral hole-burning, we show that the post annealed Yb3+ implanted LN thin film is sufficient to stabilize the Yb3+ ions in the LNOI. We further shaped LN photonic devices and demonstrate dynamical control of LN microcavities coupled to REI in a wide frequency range of 160 GHz and 5 µs switching speed. The Purcell effect of Yb3+ ions is dynamically modulated. With the Purcell enhancement, we show evidence of detecting single Yb3+ ions in LNOI cavities. We further study the spectroscopy of implanted Yb and 171Yb ions in LNOI thin film and explore the zero first-order Zeeman (ZEFOZ) transition of implanted 171Yb ions in LNOI with 8 MHz spectral hole width. Coupling quantum emitters in fast tunable photonic devices offers a platform to encode quantum information in the integration of a spectral-temporal-spatial domain and shape the waveform of the emitters.
Author(s): Jan-Wilke Henke, Max-Planck-Institut für Biophysikalische Chemie (Germany), Georg-August-Univ. Göttingen (Germany); Arslan S. Raja, Ecole Polytechnique Fédérale de Lausanne (Switzerland); Armin Feist, Max-Planck-Institut für Biophysikalische Chemie (Germany), Georg-August-Univ. Göttingen (Germany); Rui Ning Wang, Ecole Polytechnique Fédérale de Lausanne (Switzerland); Marcel Möller, Max-Planck-Institut für Biophysikalische Chemie (Germany), Georg-August-Univ. Göttingen (Germany); Junqiu Liu, Ecole Polytechnique Fédérale de Lausanne (Switzerland); Ofer Kfir, Max-Planck-Institut für Biophysikalische Chemie (Germany), Georg-August-Univ. Gottingen (Germany), Tel Aviv Univ. (Israel); Tobias J. Kippenberg, Ecole Polytechnique Fédérale de Lausanne (Switzerland); Claus Ropers, Max-Planck-Institut für Biophysikalische Chemie (Germany), Georg August Univ. Göttingen (Germany)
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Strong coupling in the interaction of free electrons with photons will allow for the exploration of various new effects. Here, we demonstrate CW-driven inelastic electron-photon scattering at a fiber-integrated high-Q Si3N4 microresonator, enabled by resonant field enhancement and electron-light phase matching. Employing energy-filtered imaging and laser detuning-dependent measurements, we characterise the electron’s interaction with the whispering gallery mode spatially and spectrally. Finally, we discuss prospects of electron-driven photon generation in the resonator. This combination of electron microscopy and integrated photonics opens up new paths for optical electron beam modulation, electron probing of nonlinear optical effects and free-electron cavity quantum optics.
Author(s): Igor L. Kurbakov, Yurii E. Lozovik, Institute of Spectroscopy RAS (Russian Federation); Nina S. Voronova, National Research Nuclear Univ. MEPhI (Russian Federation)
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We develop the Hartree-Fock-Bogoliubov description for exciton-polaritons to describe low-energy excitations at finite temperatures, accounting for the full polariton dispersion, momentum-dependent interactions and lifetimes. Beyond the mean-field approximation, the hydrodynamic form of one-body density matrix is used to describe quasicondensation. We find critical temperatures of Bose condensation and the Berezinskii-Kosterlitz-Thouless topological transition as functions of positive photon-exciton detuning, and show that the coherence length increases up to 10 times compared to zero detuning. Additionally, we show that the non-condensed fraction and the presence of dark reservoir affect the Bogoliubov sound velocity, and compare our results to the experimental findings.
OPTO Plenary Session
In person: 24 January 2022 • 8:00 AM - 10:10 AM
8:00 AM: Welcome and Opening Remarks
Sonia M. García-Blanco, Univ. Twente (Netherlands); Bernd Witzigmann, Friedrich-Alexander-Univ. Erlangen-Nürnberg (Germany)

8:05 AM: Announcement of the IBM-SPIE HBCU Faculty Accelerator Award in Quantum Optics and Photonics
Kayla Lee, IBM Research (USA)
Author(s): Hiroshi Amano, Nagoya Univ. (Japan)
In person: 24 January 2022 • 8:10 AM - 8:50 AM
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ISAMU AKASAKI, special distinguished professor of Meijo University, and distinguished university professor and emeritus professor of Nagoya University, the pioneer of blue LEDs, and the Nobel Laureate in physics, passed away from pneumonia on Thursday, April 1, 2021 at the age of 92. He was always a real pioneer. He started nitride research in 1967. At that time, blue LED research was an undeveloped area. When he moved from Matsushita Giken Co., Ltd. to Nagoya University in 1981, almost no other organizations attempted to continue with the topic. At that time, the majority of researchers determined that it was very difficult to grow single crystals, and that realizing p-type GaN was impossible. Therefore, many abandoned GaN. According to him, his situation at that time was like “going alone in the wilderness.” Today, the wilderness pioneered by Professor Isamu Akasaki is now a prosperous and fruitful field where many researchers all over the world are gathering and bringing happiness to the people. He liked the term “Frontier Electronics.” In this presentation, in addition to his memorial, today’s frontier electronics will be discussed.
Inverse designed integrated photonics (Plenary Presentation)
Author(s): Jelena Vuckovic, Stanford Univ. (United States)
In person: 24 January 2022 • 8:50 AM - 9:30 AM
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Despite a great progress in photonics over the past few decades, we are nowhere near the level of integration and complexity in photonic systems that would be comparable to those of electronic circuits, which prevents use of photonics in many applications. This lag in integration scale is in big part a result of how we traditionally design photonics: by combining building blocks from a limited library of known designs, and by manual tuning a few parameters. Unfortunately, the resulting photonic circuits are very sensitive to errors in manufacturing and to environmental instabilities, bulky, and often inefficient. We show how a departure from this old fashioned approach can lead to optimal photonic designs that are much better than state of the art on many metrics (smaller, more efficient, more robust). This departure is enabled by development of inverse design approach and computer software which designs photonic systems by searching through all possible combinations of realistic parameters and geometries. We also show how this inverse design approach can enable new functionalities for photonics, including compact particle accelerators on chip which are 10 thousand times smaller than traditional accelerators, chip-to-chip on on-chip optical interconnects with error free terabit per second communication rates, and quantum technologies.
Author(s): Andrea Blanco-Redondo, Nokia Bell Labs. (United States)
In person: 24 January 2022 • 9:30 AM - 10:10 AM
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In this talk we will discuss how to engineer the dispersion relation of photonic platforms to provide robust propagation of classical and quantum states of light. In the first part, we will unveil how to leverage the interaction of nonlinearity with higher orders of dispersion to create novel types of solitons, wave packets that propagate unperturbed for long distances. These objects have advantageous energy-width scaling laws with respect to conventional nonlinear Schrodinger solitons and show promise for applications in ultrafast lasers and integrated frequency combs. Subsequently, we will cover recent developments in topological quantum photonics. Topological photonics studies topological phases of light and leverages the appearance of robust topological edge states. We will emphasize our experimental demonstration of nonlinearly generated and topologically protected photon pairs and path-entangled biphoton states in silicon waveguide arrays. Further, we will detail our latest experiments demonstrating entanglement between topologically distinct modes, highlighting topology as an entanglement degree of freedom.
Session 3: Ultrafast Magnetism
Session Chair: Kimberley C. Hall, Dalhousie Univ. (Canada)
Author(s): Shawn Sederberg, Univ. of Ottawa (Canada)
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Our ability to structure magnetic fields in space and time is limited by the electrical conductors and superconductors used to carry currents in electromagnets. In this work, we explore the possibility to transfer spatial and temporal structure from femtosecond laser pulses to currents in solids and gases via coherent control. In particular, we demonstrate how structured light can be used to sculpt and reconfigure complex current arrangements including ring currents in solids and gases. I will discuss our experimental efforts to use these currents for reconfigurable optoelectronic circuitry, to control THz bandwidth magnetic fields, and to serve as active metasurfaces for generating THz impulses with exotic spatio-temporal structure.
Author(s): Dmytro Afanasiev, Univ. Regensburg (Germany); Yaroslav Blanter, Technische Univ. Delft (Netherlands); Rostislav V. Mikhaylovskiy, Lancaster Univ. (United Kingdom); Alexey V. Kimel, Radboud Univ. Nijmegen (Netherlands); Andrea D. Caviglia, Technische Univ. Delft (Netherlands)
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Here we show that light-driven phonons can be utilized to coherently manipulate macroscopic magnetic states. Intense mid-infrared electric field pulses, tuned to resonance with a phonon mode of the archetypical antiferromagnet DyFeO3, induce ultrafast and long-living changes of the fundamental exchange interaction between rare-earth orbitals and transition metal spins. Non-thermal lattice control of the magnetic exchange, defining the very stability of the macroscopic magnetic state, allows us to perform picosecond coherent switching between competing antiferromagnetic and weakly ferromagnetic spin orders. Our discovery emphasizes the potential of resonant phonon excitation for the manipulation of ferroic order on ultrafast timescales.
Author(s): Viatcheslav Vanyukov, Univ. of Eastern Finland (Finland); Gennady M. Mikheev, Tatyana Mogileva, Institute of Applied Mechanics of RAS (Russian Federation); Yuri P. Svirko, Univ. of Eastern Finland (Finland)
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Wе dеmonstrаtе thаt thе tеmporаl profilе of thе trаnsvеrsе nаnosеcond photovoltаgе pulsе gеnеrаtеd in thе thin sеmiconducting CuSе/t-Sе nаnocompositе film undеr irrаdiаtion with еllipticаlly polаrizеd fеmtosеcond pulsе is dеtеrminеd by thе intеrplаy of linеаr аnd circulаr photocurrеnts. Thеsе photocurrеnts hаvе diffеrеnt durаtions indicаting thе dеpеndеncе of thе rеlаxаtion timе of thе photogеnеrаtеd cаrriеrs on thеir spin. Thе intеrplаy of photocurrеnt rеsults in thе gеnеrаtion of еithеr unipolаr or bipolаr pulsе with tеmporаl profilе dеpеndеnt on thе dеgrее of thе circulаr polаrizаtion of thе еxcitаtion bеаm thаt onе cаn control by rotаting thе fаst аxis of thе quаrtеr-wаvе plаtе.
Author(s): Peter C. Johnsen, Christian D. Gentry, JILA (United States); Justin M. Shaw, Hans T. Nembach, Tom Silva, National Institute of Standards and Technology (United States); Henry C. Kapteyn, Margaret M. Murnane, JILA (United States)
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The measurement and control of nanoscale spin dynamics is essential for the understanding and development of quantum materials. We present a new instrument along with precise spectroscopic measurements of ultrafast magnetic phenomena using extreme ultraviolet high harmonic sources. Our unique instrument allows us to optically control and probe spin dynamics of complex magnetic materials with element specificity on few-femtosecond timescales on up.
Session 4: Quantum Emitters
Session Chair: Shawn Sederberg, Univ. of Ottawa (Canada)
Author(s): Mario Agio, Univ. Siegen (Germany), Consiglio Nazionale delle Ricerche (Italy), European Lab. for Nonlinear Spectroscopy (Italy); Haritha Kambalathmana, Assegid M. Flatae, Univ. Siegen (Germany)
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We discuss theoretical and experimental results on the ultrafast detection of quantum emitters. We employ nano-antennas, specifically gold nanocones, to accelerate the spontaneous emission rate of silicon-vacancy color centers in diamond by orders of magnitude to generate single photons with picoseconds timescales. Moreover, we implement an optical Kerr shutter under tight focusing to be able to detect such ultrafast single photons with time resolutions down to a few hundreds of femtoseconds.
Author(s): Galan Moody, Univ. of California, Santa Barbara (United States)
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The search for an ideal single-photon source has generated significant interest in discovering novel emitters in materials as well as developing new manipulation techniques to gain better control over the emitters’ properties. Quantum emitters in atomically thin 2D materials have proven very attractive with high brightness, operation under ambient conditions, and the ability to be integrated with a wide range of electronic and photonic platforms. In this presentation, I will highlight some of the recent advances in quantum light generation from 2D materials, focusing on hexagonal boron nitride and transition metal dichalcogenides (TMDs). I will discuss our efforts in engineering and deterministically creating arrays of tunable quantum emitters in 2D materials, their electrical excitation, and their integration with photonic devices.
Author(s): Grant R. Wilbur, Ali Binai-Motlagh, Ajan Ramachandran, Dalhousie Univ. (Canada); Sabine O'Neal, imec USA - Florida (United States); Dennis G. Deppe, CREOL, The College of Optics and Photonics, Univ. of Central Florida (United States); Kimberley C. Hall, Dalhousie Univ. (Canada)
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Semiconductor quantum dots (QDs) may be applied to solid-state quantum emitters of interest for quantum light sources or nodes in distributed quantum networks. For such emitters, resonant optical driving results in the highest degree of photon indistinguishability, but leads to the need to reject scattered light from the laser used to drive the emitter. In this work, we apply femtosecond pulse shaping techniques to the development of quantum state inversion strategies for QD emitters that optimize fidelity and source brightness. The control protocols we have developed would be applicable to a wide range of solid-state QE systems.
Author(s): Lukas Hanschke, Univ. Paderborn (Germany); Lucas Schweickert, KTH Royal Institute of Technology (Sweden); Juan Camilo López Carreño, Univ. of Wolverhampton (United Kingdom); Eva Schöll, Univ. Paderborn (Germany); Katharina D. Zeuner, Thomas Lettner, KTH Royal Institute of Technology (Sweden); Eduardo Zubizarreta Casalengua, Univ. of Wolverhampton (United Kingdom); Marcus Reindl, Saimon Filipe Covre da Silva, Johannes Kepler Univ. Linz (Austria); Rinaldo Trotta, Johannes Kepler Univ. Linz (Italy); Jonathan J. Finley, Walter Schottky Institut (Germany); Armando Rastelli, Johannes Kepler Univ. Linz (Austria); Elena del Valle, Univ. Autónoma de Madrid (Spain); Fabrice P. Laussy, Univ. of Wolverhampton (United Kingdom); Valery Zwiller, KTH Royal Institute of Technology (Sweden); Kai Müller, Walter Schottky Institut (Germany); Klaus D. Jöns, Univ. Paderborn (Germany)
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We present measurements that prove that the simultaneous observation of sub-natural linewidth and antibunching of resonance fluorescence is not possible. High-resolution spectroscopy reveal the sharp spectral feature of the weak driving regime with a vanishing component of incoherently scattered light. Filtering the emission in the order of the Fourier limited linewidth leads to the loss of antibunching in the correlation measurement. Our theoretical model identifies two-photon interference between the coherent and incoherently scattered light as the origin of antibunching. This prefigures schemes to achieve a source of single photons with sub-natural linewidth.
Author(s): Friedrich Sbresny, Lukas Hanschke, Technische Univ. München (Germany); Eva Schöll, Univ. Paderborn (Germany); William Rauhaus, Jonathan J. Finley, Technische Univ. München (Germany); Klaus D. Jöns, Univ. Paderborn (Germany); Kai Müller, Technische Univ. München (Germany)
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We propose a scheme for the generation of highly indistinguishable single photons using semiconductor quantum dots and demonstrate its performance and potential. The scheme is based on the resonant two-photon excitation of the biexciton followed by stimulation of the biexciton to selectively prepare an exciton. Quantum-optical simulations and experiments are in good agreement and show that the scheme provides significant advantages over previously demonstrated excitation methods. Specifically, the scheme allows for ultra-low multi-photon error rates, high indistinguishability, high brightness and programmable linear polarization.
Author(s): Hendrik Rose, Univ. Paderborn (Germany); Olga V. Tikhonova, M. V. Lomonosov Moscow State Univ. (Russian Federation); Torsten Meier, Polina R. Sharapova, Univ. Paderborn (Germany)
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We consider an electronic three-level system that is resonantly excited with two single-mode quantum fields. This system is treated with a Jaynes-Cummings type model, leading to a fully-quantized system, where quantum correlations are found to arise during the interaction. We present a detailed insight into the formation and physical nature of these correlations. We use the cluster-expansion approach to obtain a quantitative measure for the correlation between two quantum fields, allowing us to examine contributions of different order N-particle correlations. Numerical results for the correlations between the two quantum fields are presented and discussed.
Session 5: Carrier Dynamics in Semiconductors and 2D Materials
Session Chair: Galan Moody, Univ. of California, Santa Barbara (United States)
Author(s): Elsa Abreu, ETH Zurich (Switzerland); Danylo P. Babich, Etienne Janod, Institut des Matériaux Jean Rouxel (France); Sarah Houver, Lab. Matériaux et Phénomènes Quantiques (France), ETH Zurich (Switzerland); Benoît Corraze, Laurent Cario, Institut des Matériaux Jean Rouxel (France); Steven L. Johnson, ETH Zurich (Switzerland), Paul Scherrer Institut (Switzerland)
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Quasi-dc electric fields of several hundred kV/cm can currently be generated with ultrashort pulses in the low frequency or THz range, enabling the investigation of the sub-picosecond dynamics of the electric field driven Mott transition. THz pulses can also be used to track the Drude conductivity response of the material directly, without the need to deposit any electrical contacts on the sample. We will present our results on THz driven dynamics in GaTa4Se8, a Mott insulator which exhibits clear electrical Mott transitions.
Author(s): Elisabetta Collini, Univ. degli Studi di Padova (Italy)
Author(s): Lukas Gierster, Humboldt-Univ. zu Berlin (Germany), Fritz-Haber-Institut der Max-Planck-Gesellschaft (Germany); Sesha Vempati, Indian Institute of Technology Bhilai (India), Fritz-Haber-Institut der Max-Planck-Gesellschaft (Germany); Julia Stähler, Humboldt-Univ. zu Berlin (Germany), Fritz-Haber-Institut der Max-Planck-Gesellschaft (Germany)
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Band bending at semiconductor surfaces induced by e.g. chemical doping can create metallic surfaces with properties not found in the bulk, such as high electron mobility, magnetism or superconductivity. Optical generation of such metallic surfaces on ultrafast timescales would be appealing for high-speed electronics. We demonstrate the ultrafast generation of a metal at the surface of ZnO upon photoexcitation. Compared to known ultrafast photoinduced semiconductor-to-metal transitions that occur in the bulk of inorganic semiconductors, the metallization of the ZnO surface is launched by 3–4 orders of magnitude lower photon fluxes. Using time- and angle-resolved photoelectron spectroscopy, we show that the phase transition is caused by photoinduced downward surface band bending due to photodepletion of donor-type deep surface defects. These findings present a general route for controlling surface-confined metallicity on ultrafast timescales.
Author(s): Ermin Malic, Philipps-Univ. Marburg (Germany)
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Monolayer transition metal dichalcogenides (TMDs) exhibit a remarkable excitonic landscape including bright and a variety of dark exciton states. Solving 2D material Bloch equations for excitons, phonons and photons, we obtain a microscopic access to the interplay of optics, ultrafast dynamics and diffusion of excitons in TMDs. In joint theory-experiments studies we shed light on the importance of momentum-dark excitons in low-temperature photoluminescence spectra, non-equilibrium exciton dynamics visualized in tr-ARPES experiments, temperature-resolved exciton-exciton annihilation processes, phonon-driven dissociation of excitons [4], and accelerated hot-exciton diffusion. The gained microscopic insights into the spatiotemporal exciton dynamics are crucial for understanding and controlling many-particle phenomena governing exciton optics, dynamics and transport in technologically promising 2D materials.
Author(s): Guan-Jie Huang, National Taiwan Univ. (Taiwan); Hao-Yu Cheng, Academia Sinica (Taiwan); Yu-Lung Tang, National Taiwan Univ. (Taiwan); Hotta Ikuto, Junichi Takahara, Osaka Univ. (Japan); Kung-Hsuan Lin, Academia Sinica (Taiwan); Shi-Wei Chu, National Taiwan Univ. (Taiwan)
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In this study, we propose the concept of generating transient nonlinearity via nonlinear carrier lifetime variation based on Auger recombination in silicon nanostructures. The nonlinear Auger lifetime variation creates a common crossing point for all pump-probe transient traces at different pump fluences, presenting a fluence-independent property. Furthermore, we observe that sub-linear and super-linear responses exist before and after the crossing point, revealing an unconventional temporal tunability of Auger-induced transient nonlinearity. Leveraging the combination of a laser scanning microscope and pump-probe technique, these temporally transient nonlinear behaviors are applicable to spatial resolution enhancement beyond the diffraction limit.
Author(s): Christopher B. Marble, Kassie S. Marble, Vladislav V. Yakovlev, Texas A&M Univ. (United States)
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Silicon optoelectronics devices have been explored for near-IR telecom applications. In the mid-IR regime, group IV optoelectronic devices (silicon and/or germanium based) could one day serve as waveguides, nonlinear media for wavemixing, and platforms for lab-on-chip chemical sensors. Nonlinear absorption effects in these materials limit potential applications. In this study, we explore the nonlinear absorption of group IV semiconductors and how it results from a combination of multiphoton absorption and electron-hole pair generation. We seek to understand and decouple the processes by operating in the femtosecond regime, where electron-hole pair time dynamics is negligible, for mid-IR excitation wavelengths up to 9 μm.
Session 6: Ultrafast Structural Dynamics
Session Chair: Abdulhakem Y. Elezzabi, Univ. of Alberta (Canada)
Author(s): Markus Gühr, Univ. Potsdam (Germany)
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Molecules selectively transform the energy of absorbed photons into other energetic forms like heat, chemical bonds, or transferred charges with high quantum efficiency. This conversion process often occurs under the breakdown of the Born-Oppenheimer approximation. Ultrafast x-ray pulses offer new possibilities to investigate the coupled motion of electrons and nuclei with site and element selectivity. We show different experimental examples for x-ray probing of photoexcited molecules. We use ultrafast Auger spectroscopy for local bond changes, x-ray absorption spectroscopy for detecting lone pair orbitals in the conversion, and x-ray photoelectron spectroscopy to deduce charge motion within the excited molecule.
Author(s): Paul E. Barclay, Univ. of Calgary (Canada)
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Nanoscale photonic devices can be engineered to enable strong interaction between mechanical resonances and co-located optical fields. This interaction can be harnessed for sensitive displacement measurement, force sensing, and more recently, torque sensing. Using photonic crystal split beam and slot mode cavities, we have demonstrated detection of torsional motion at frequencies spanning MHz to nearly a GHz. In this talk we will show how this sensitive detection allows probing of the dynamics of nanoscale magnetic structures, opening new avenues for experiments in condensed matter physics.
Author(s): Jigang Wang, Iowa State Univ. of Science and Technology (United States)
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The recent development of nonlinear coherent spectroscopy and microscopy tools facilitates discovering and controlling topologically protected states (TPSs) by light at a THz clock rate. In this talk, I will discuss strategic advantages, with help of some recent examples from our research, of implementing the nonlinear optics approach to measure, manipulate and harvest topological photocurrent, chiral bands and phononic symmetry switches in TPSs, including discoveries of light-induced formation of Dirac and Weyl semimetals using infrared and Raman phonon coherences, ultrafast manipulation of topological surface transport and imaging of topological strip junctions at THz-nm scales.
Author(s): Sebastian Rieger, Jacek K. Stolarczyk, Jochen Feldmann, Ludwig-Maximilians-Univ. München (Germany)
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Bismuth oxyiodide (BiOI) is a promising material for photocatalysis with intriguing optical and structural properties. We demonstrate that excitation by a femtosecond laser pulse creates coherent phonons inducing a time-variant oscillating modulation of the optical density. The two underlying frequencies originate from vibrations along the stacking direction of oppositely charged layers in BiOI. This is consistent with a subpicosecond charge separation driven by a built-in dipolar field. This partially screens the field, launching coherent phonons. Our results demonstrate the presence of an electric field and show its role in efficient charge separation that is crucial for photocatalytic applications of BiOI.
Session 7: Nonlinear Optics
Session Chair: Jigang Wang, Iowa State Univ. of Science and Technology (United States)
Author(s): Bahram Jalali, Tingyi Zhou, UCLA Samueli School of Engineering (United States); Fabien Scalzo, Univ. of California, Los Angeles (United States)
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We report a new concept in hardware acceleration of AI that exploits femtosecond pulses for both data acquisition and computing. Data is first modulated onto the spectrum of a supercontinuum laser. Nonlinear optical propagation then projects the data into an intermediate space in which data classification accuracy is enhanced. This nonlinear optical kernel operation improves the linear classification results similar to a traditional numerical kernel (such as the radial-basis-function) but with orders of magnitude lower latency. The performance is data-dependent due to the limited degrees of freedom in the optical part of the system.
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We review the use of machine learning techniques in ultrafast photonics applications with emphasis on fiber-optics systems. In particular, we discuss how neural networks can be used to extract quantitative time-domain information in the development of nonlinear instabilities from spectral intensity measurements. We also show how neural networks can be efficiently applied to predict nonlinear dynamics in optical fibres for a wide range of scenarios, from pulse compression to ultra-broadband supercontinuum generation in both single and multimode fibers.
Author(s): Zhanghua Han, Shandong Normal Univ. (China)
Author(s): Guifang Wang, Shantou Univ. (China); Wolf-Rüdiger Hannes, Univ. Paderborn (Germany); Marcelo Ciappina, Guangdong Technion-Israel Institute of Technology (China); Huynh Thanh Duc, Vietnam Academy of Science and Technology (Vietnam); Xiaohong Song, Weifeng Yang, Shantou Univ. (China); Torsten Meier, Univ. Paderborn (Germany)
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We analyze high-harmonic generation resulting from the nonlinear interaction of solid samples with very strong Terahertz pulses by solving the semiconductor Bloch equations. We compare the length and velocity gauges and demonstrate that the latter is advantageous. We reveal that elastic scattering of electrons and holes strongly influences their recombination. We link the backward (forward) scattering to Van Hove singularities (with critical lines in the band structure), thereby establishing a mapping between them and the harmonic spectrum. We also show that under proper conditions, the even-order harmonics, polarized perpendicular to the driving field, originate predominantly from the Berry curvature.
Author(s): Brett N. Carnio, Eric Hopmann, Basem Y. Shahriar, Abdul Y. Elezzabi, Univ. of Alberta (Canada)
Session 8: Ultrafast Aspects of Optical Sources
Session Chair: Markus Gühr, Univ. Potsdam (Germany)
Author(s): Frank Jahnke, Stephan Michael, Michael Lorke, Univ. Bremen (Germany)
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Increased modulation speed in quantum-dot lasers is possible by means of a tunnel-injection design. The concept was introduced to improve the dynamical properties of semiconductor lasers by avoiding the problem of hot carrier injection, which increases the gain nonlinearity thereby limiting the modulation capabilities. Cold carriers are efficiently provided via an injector quantum well that is tunnel coupled to excited QD states. We study the ultrafast carrier population dynamics in tunnel-injection lasers by comparing LO-phonon-assisted tunneling processes and Coulomb-scattering-assisted processes.
Author(s): Frederik Lohof, Christopher Gies, Univ. Bremen (Germany)
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The absence of strong losses in high-beta nanolasers makes the identification of the onset of lasing difficult to pinpoint, as the input-output characteristics can become almost thresholdless [1]. The second-order photon correlation function g2(0) has become a valuable tool to assess the coherence properties of nanolasers, as its transition to a value of 1 clearly marks the laser threshold. Most measurements of the zero-delay-time autocorrelation function involve temporal averaging over g2(tau) due to the finite time resolution of the photon detectors. In the past, a generalized Siegert relation has been used to approximately obtain g2(tau). Using full quantum-optical two-time calculations, we address the question in how far it can be used in the partially coherent regime of conventional nanolasers that show a soft transition to lasing [1], and in few-emitter nanolasers that operate close to or in the regime of strong light-matter coupling. [1] Laser & Photonics Review 14, 2000065
Author(s): Valerio Di Giulio, ICFO - Institut de Ciències Fotòniques (Spain); Ofer Kfir, Tel Aviv Univ. (Israel), Max-Planck-Institut für Biophysikalische Chemie (Germany); Claus Ropers, Max-Planck-Institut für Biophysikalische Chemie (Germany), Georg-August-Univ. Göttingen (Germany); F. Javier García de Abajo, ICFO - Institut de Ciències Fotòniques (Spain), Institució Catalana de Recerca i Estudis Avançats (Spain)
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We explore the role that the electron wave function plays in cathodoluminescence (CL) emission when an external laser pulse is synchronized with the electron probe at the sample. We show that the the far-field emission is composed by coherent and incoherent contributions where the latter can only be modified by changing the electron density profile. In particular, shaped electrons lead to a partial suppression of the CL signal while its complete cancellation can be only achieved in the point-particle limit. We believe that our results open new routes toward coherent control of optical excitations at the atomic scale as well as toward a new method of studying ultrafast phenomena with a time resolution only limited by the width of the spectral window in the CL measurement.
Author(s): Rui Zhou, Hemang Jani, The Univ. of Alabama in Huntsville (United States); Yijun Zhang, Yunsheng Qian, Nanjing Univ. of Science and Technology (China); Lingze Duan, The Univ. of Alabama in Huntsville (United States)
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We report a comparative study of the ultrafast response of a uniform-doped and a gradient-doped GaAs photocathode. A generalized diffusion-drift model, which adds a built-in electric field to a carrier diffusion model to incorporate the carrier drift, is developed and used to predict the ultrafast transient behaviors of photoelectrons in uniform/gradient-doped photocathodes. The experimental data is measured using pump-probe reflectometry (PPR) and compared to the theoretical predictions. Comparisons indicate that the theoretical model can offer an appropriate physical picture of carrier transportation inside GaAs photocathodes of different doping profiles. It also enables the evaluation of device parameters via PPR measurement.
Author(s): Sara Meir, Moti Fridman, Bar-Ilan Univ. (Israel)
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We analyze the joint spectral function of correlated photons. We show how amplifiers change the correlation and how it is possible to restore this correlation by neglecting some of the peaks in the signals. We analyze all the peaks in the time and spectrum and study the influence of each of them on the joint spectral function. We found that it is possible to obtain any joint spectral function by neglecting or adding specific peaks in the spectrum. In the talk, we will describe our results which are based on single-shot ultrafast measurements of both the spectrum and the time of spontaneous four-wave mixing generation. We will also show numerical and analytical results which support our claims.
Session 9: 2D Materials
Session Chair: Frank Jahnke, Univ. Bremen (Germany)
Author(s): Ryo Shimano, The Univ. of Tokyo (Japan)
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We have investigated the light-induced phase transition into a hidden metastable phase in a charge density wave phase in a layered transition metal dichalcogenide compound, 3R-TaSe2, through the direct excitation of amplitude mode by using intense terahertz pulse sources. Appearance of an insulating-like metastable state is observed, as manifested by the opening of a gap in the optical conductivity spectrum in the terahertz frequency range. The formation of the gap synchronizes with the oscillation of the amplitude mode of the equilibrium CDW, indicating the intimate interplay between the hidden phase and the equilibrium CDW state.
Author(s): Ziliang Ye, The Univ. of British Columbia (Canada)
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Different stackings in van der Waals materials offer a new opportunity to create and discover novel physical properties such as ferroelectricity. Recently we found a spontaneous polarization in a van der waals semiconductor with a stacking order that breaks the inversion symmetry. In a graphene contacted device, the spontaneous polarization induces a strong photovoltaic effect. The pv current is driven by the depolarization field and mainly composed of photo-excited electrons. Since the polarization is nearly uniform in the naturally existing bulk material, our observation provides a scalable way to utilize the emergent polarization in 2D materials.
Author(s): Ting Cao, Univ. of Washington (United States)
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This talk will show our recent theoretical and computational studies of new exciton physics in monolayer transition metal dichalcogenides. By developing a first-principle method based on many-body perturbation theories, we find that the photoelectrons from excitons hold unique energy dispersions and spectra weights, which unveil the fundamental physical properties of the excitons. The theoretical findings agree well with the experimentally measured pump-probe photoemission spectra of excitons in monolayer WSe2 (Science 370, 1199 (2020) and Science Advances 7, eabg0192 (2021)). We then demonstrate a valley- and spin-selective excitonic energy relaxation pathway, which leads to novel ultrafast dynamics in monolayer transition metal dichalcogenides. We further connect our theoretical discoveries to experimental results and explore their potential applications.
Author(s): Nahid Talebi Sarvari, Christian-Albrechts-Univ. zu Kiel (Germany)
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Strong couplings between quantum particles lead to novel quasi-particles with exotic properties. Particularly interactions between photons and room temperature excitons in van der Waals materials, form exciton-polaritons under certain circumstances, with applications in Bose-Einstein condensation or optoelectronics. Here, we demonstrate that exciton-polaritons can exist in Bi2Se3 thin films, in the form of surface and edge hyperbolic exciton polaritons. We also show the existence of exciton-polaritons in WSe2 thin films and demonstrate, using cathodoluminescence spectroscopy, that the coupling strength between photons and excitons could be further controlled using Bloch Plasmons allowing to tuning the density of the photonic states into an unprecedented extreme level.
Conference Chair
Technische Univ. Dortmund (Germany)
Conference Chair
Univ. of Alberta (Canada)
Program Committee
West Virginia Univ. (United States)
Program Committee
Keshav Dani
Okinawa Institute of Science and Technology Graduate Univ. (Japan)
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Jeff Davis
Swinburne Univ. of Technology (Australia)
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Dalhousie Univ. (Canada)
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Univ. Regensburg (Germany)
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Arizona State Univ. (United States)
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Ulsan National Institute of Science and Technology (Korea, Republic of)
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The Univ. of Texas at Austin (United States)
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Carl von Ossietzky Univ. Oldenburg (Germany)
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James Lloyd-Hughes
The Univ. of Warwick (United Kingdom)
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Univ. Paderborn (Germany)
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Frank J. Meyer zu Heringdorf
Univ. Duisburg-Essen (Germany)
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Univ. Bielefeld (Germany)
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Pascal Ruello
Le Mans Univ. (France)
Program Committee
The George Washington Univ. (United States)
Program Committee
Institut Lumière Matière (France)
Program Committee
Kam Sing Wong
Hong Kong Univ. of Science and Technology (Hong Kong, China)