This PDF file contains the front matter associated with SPIE Proceedings Volume10548, including the Title Page, Copyright information, Table of Contents, Introduction, and Conference Committee listing.

We present a new concept of the homodyne interferometric adaptive detection of optical phase modulation. To ensure adaptivity, i.e. stabilization of the interferometer operation point, we utilize the phase memory of a two-level quantum system, resonantly illuminated with the information bearing signal wave. Phase modulation of the transmitted signal wave transforms into the intensity modulation via interference with the collinearly propagating dipole radiation of the excited two-level system. The latter acts like a reference wave since it has a phase corresponding to that of the signal wave but averaged over the transverse relaxation time T₂ of the quantum system. Experimental demonstration with the acetylene-filled hollow-core micro-structured optical fiber at the communication wavelength of 1530nm of the acetylene P9 absorption line is presented. It is shown that the response to the introduced phase modulation is quadratic when the acetylene inhomogeneously broadened absorption line is excited in its center and is a linear one if it is excited at one of the absorption line sides.

The key figures of merit for integrated optical components include the device footprint and operating energy consumption, both being major contributors to the purchase and operating cost, respectively. Slow light in silicon photonic crystal (PhC) devices has the potential to significantly reduce both, through enhanced light matter interactions, for both linear and non-linear optics applications. However, for all applications a precise control over the slow-down factor and reduced optical losses are paramount. In this paper, we present our work on various low-loss slow light systems based on PhC technology. We discuss the ability to control the group index and propagation loss of a PhC waveguide through appropriate device design - dispersion and loss engineered waveguides. This control, providing us with a free choice of group index ranging from 5 to 100, has already led to a range of non-linear optical applications, such as third harmonic generation, four-wave mixing and photon pair generation. We extend this approach to kagome lattice based PhCs and show that group indices exceeding 100 000 are possible in photonic crystal based geometries.

We further discuss the post-fabrication control over slow light in PhC waveguides. Here both permanent, passive control is possible - through post-processing of the PhC devices - and adaptable, active control, through electro-optic or thermo-optic tuning. We apply the latter to a coupled cavity geometry that displays a transmission peak analogous to electromagnetically induced transparency and show a tuneable delay of 300ps with a delay loss of approximately 15dB/ns.

We present an approach for optimal interfacing with coupled resonator optical waveguides (CROWs). The interfacing section constitute an additional small set of cavities with varying coupling coefficients at edges of the CROW in order to match its impedance with that of the I/O waveguides. Efficiencies exceeding 99.9% are shown to be possible over a bandwidth which is larger than 50% of that of the CROW. We study the relations between the number of resonators comprising the interface section and its overall performances.

We studied a miniature optical fiber sensor based on in-line Fabry-Perot interferometer for strain measurement. The sensor was fabricated by splicing a section of hollow core tube (HCT) between two single mode fibers. The reflective spectrum of the interferometer exhibits a number of resonance wavelength dips owing to destructive interference of two reflective lights. The experiment results demonstrate that, as the strain increased, the resonance wavelength exhibits a redshift behavior. The maximal strain sensitivity obtained by linear fitting is 4.55pm/με. The device proposed has high potential in construction engineering, industry production, and high speed rail due to its merits of electromagnetic immunity, miniature structure and ease of fabrication.

Whispering-gallery microresonators are well suited for use as sensors. For example, fluid analytes can be sensed through their effect on the refractive index or by their optical absorption. The former results in a frequency shift of a whispering-gallery mode (WGM); the latter changes the WGM’s intensity profile, and can be even more sensitive than the former. WGMs are typically excited by coupling of light from a tapered fiber. It has recently been demonstrated that using a non-adiabatic tapered fiber can produce a Fano resonance whose asymmetric shape can enhance the sensitivity of refractive-index sensing. The non-adiabatic taper allows the incoming light to be distributed between two fiber modes that interfere when exciting a single WGM, thereby producing the asymmetric resonance. However, just as absorption sensing can be more sensitive than index sensing, its enhancement by using a non-adiabatic taper can be greater as well. This enhancement is demonstrated theoretically here, and experiments for confirmation are underway.

We provide a novel arithmetic for the calculation of the transmission equation in a structure based on the add-drop resonator. Moreover this method can be applied on all the structures containing add-drop resonators or analogous configurations to simplify the calculation and the light path analysis. The characteristics of the transmission spectra in add-drop interferometer with two different kinds of curves are analyzed. We find out the reason for the different transmission spectra and draw an analogy with the under coupling, over coupling, and critical coupling. These results will provide some useful information and a new track to analyze the structures in this field.

We review our last work on dispersion-engineered heterogeneous multicore fiber links designed to act as tunable true time delay lines for radiofrequency signals. This approach allows the realization of fiber-distributed signal processing in the context of fiber-wireless communications, providing both radiofrequency access distribution and signal processing in the same fiber medium. We show how to design trench-assisted heterogeneous multicore fibers to fulfil the requirements for sampled true time delay line operation while assuring a low level of crosstalk, bend sensitivity and tolerance to possible fabrication errors. The performance of the designed radiofrequency photonic delay lines is evaluated in the context of tunable microwave signal filtering and optical beamforming for phased array antennas.

The possibility of using integrated photonics to scale multiple optical components on a single monolithic chip offers transformative advantages in fields such as communications, computing, bioengineering, and sensing. However, today’s integrated photonic circuits are rudimentary compared to the complexity of modern electronic circuits. Any advancements to efficiently integrate new photonic functionalities bring us closer to replicate the enormous impact of electronic integrated circuits. Slow light propagation in chip-integrated nanophotonic structures with engineered band dispersion is a highly promising approach for controlling the relative phase of light and for enhancing optical nonlinearities on a chip. A primary goal in this field is to achieve devices with large, approximately constant group index (n_g) over the largest possible bandwidth, thereby enabling multimode and pulsed operation. We present an experimental record high group-index-bandwidth product (GBP) in genetically optimized coupled-cavity-waveguides (CCWs) designed by L3 photonic crystal nanocavities. The resulting designs were realized in SOI buckling-free suspended slabs with CCWs integrating up to 800 coupled nanocavities. The samples were characterized by measuring the CCW transmission, the mode dispersion through Fourier-space imaging, and ng via Mach-Zehnder interferometry. Various nanocavity designs were investigated, with theoretical n_g ranging from 37 to 100. Record high GBP = 0.47 was demonstrated over a bandwidth of 19.5 nm with a homogeneous flat-top transmission profile (variations lower than 10 dB) and losses below 56 dB/ns. Our results open the path towards building enhanced slow-light-based devices such as of slow-light-enhanced spectroscopic interferometers and single-photon buffers.

An attractive feature of surface plasmons (SPs) is the sub-wavelength characteristics, especially the SPs in two dimensional Dirac systems. In mid-infrared region, the wave vectors of graphene plasmons (GPs) can be two orders larger than that in vacuum, which have potential applications in optical imaging. Here, we propose a scheme that combining the GPs and structured illumination microscopy to realize a nanometer-scale microscopy. This scheme also takes advantage of the other two exciting properties of GPs, i.e., tunability and low loss. The microscopy works in the linear regime and can be used in bioimaging.

This Conference Presentation, “Sub-angstrom precise resonant nanophotonic devices at the optical fiber surface,” was recorded at SPIE Photonics West 2018 held in San Francisco, California, United States.

A theoretical analysis of this little-studied resonator is performed, including a study of its sensitivity as a gyroscope and of transmission spectrum properties. When all its free parameters are optimized (the coupling ratio of the 3x3 coupler, the probe laser wavelength, and the length mismatch between the rings), this sensor is predicted to have the exact same maximum possible rotation sensitivity as a resonant fiber optic gyroscope (RFOG) with the same ring radius and fiber loss, for either a triangular or a planar a 3x3 fiber coupler. Changing the length mismatch (and re-adjusting the coupling ratio to maximize the sensitivity) has very little impact on the best sensitivity: all it does is redistribute the circulating light between rings, but the total number of recirculations is essentially unchanged, and so is the sensitivity. A second type of double-ring resonator is studied in which the output is collected via a 2x2 coupler placed on one of the rings. This two-coupler double-ring resonator gyroscope is found to have a larger rotation sensitivity than a two-coupler RFOG. For exceedingly small loss, the sensitivity enhancement is vanishingly small. For a ring loss of 1 dB, the enhancement is 1.8-fold. As the loss is increased, the enhancement increases asymptotically to either ~2.11 (triangular coupler) or ~1.78 (planar coupler), but the loss is then too high for either sensor to be practical. For small loss, the sensitivity of a two-coupler RFOG is 4 times lower than that of a conventional (one-coupler) RFOG. A two-coupler double-ring resonator gyroscope therefore never surpasses a single-coupler RFOG in sensitivity, but for applications requiring an additional 2x2 coupler, a two-coupler double-ring resonator has a higher rotation sensitivity than a twocoupler RFOG.

Due to the Kramers-Kronig relations, the gain-loss transfer function of a medium is connected to its dispersion behavior. A possibility to artificially generate gains and losses in a medium is the nonlinear effect of stimulated Brillouin scattering (SBS). The special advantage of SBS is that it offers a very narrow linewidth, which additionally can be broadened and adapted to the application by a modulation of the SBS pump wave, it is the nonlinear effect with the smallest threshold and optical fibers or integrated chips can be used as the nonlinear medium. Thus, the SBS offers the possibility to artificially engineer the dispersion of a medium, which can be used for many possible applications in engineering and science. Here, after a brief discussion of dispersion engineering with SBS we will emphasize two applications of this kind of dispersion engineering for additional noise-free microwave filters and the storage of light.

The phase shift occurred by optical waves in nonlinear interaction may be considered as phase shift resulted from a nonlinear refractive index. Consequently, a spectrum of the nonlinear phase shift in non-degenerate in frequency interactions represents nonlinear dispersion. Thus the nonlinear interaction with such dispersion may be used to achieve slow and fast light. The phase-conjugate reflectivity in photorefractive four-wave mixing may reveal spectrum with two maxima, which are located symmetrically with respect to zero frequency detuning. A complicated nonlinear dispersion corresponds to such reflectivity spectrum. Qualitative analysis of the nonlinear dispersion suggests unusual behavior when the nonlinear effect, i.e., delay of the light pulse, may decrease with increase of nonlinear coupling strength. The numerical calculations confirm such a nontrivial behavior. The experimental conditions are found, for which the delay of the phase-conjugate pulse decreases when the coupling strength increases. The conclusions of the theoretical analysis are confirmed experimentally for photorefractive four-wave mixing in barium titanate.

A new scheme for ultrasensitive laser gyroscopes that utilizes the physics of exceptional points will be presented. By exploiting the properties of such non-Hermitian degeneracies, we show that the rotation-induced frequency splitting becomes proportional to the square root of the gyration speed (√𝛀)- thus enhancing the sensitivity to low angular rotations by orders of magnitudes. In addition, at its maximum sensitivity limit, the measurable spectral splitting is independent of the radius of the rings involved. Our work paves the way towards a new class of ultrasensitive miniature ring laser gyroscopes on chip.

Optical Isolators are important components of photonic circuits and require breaking of time inversion symmetry. Usually it is achieved with magnetic field but recent years have seen an effort directed toward development of magnetic –field –free optical isolators, based on temporal modulation and/or optical nonlinearity. In this talk various non-magnetic schemes will be compared and the case will be made for the optical isolator based on second and third order nonlinearities that have high degree of isolation and dynamic range

Restricted to picosecond scale time gaps, the previous reported temporal cloaking schemes are hardly possible for practical applications. In this paper, we report a nanosecond scale temporal cloaking regime based on the fast/slow light effect in unbalanced fiber Mach-Zehnder interferometers. By exerting a radio frequency modulation onto the probe light, we broke through the gap time limit. A time gap up to 5.3ns was created and experimentally observed. The modulation signal in the time gap was concealed efficiently. Realizing nanosecond time gaps is critical for potential applications of temporal cloaking, such as secure communication and signal processing. This solution may push this fascinating idea into reality

We describe the operation and results of our first generation zero field optically pumped magnetometer (OPM) developed for biomedical applications. The OPM technology is one of the most promising non-cryogenic candidates to replace superconducting quantum interference device (SQUID) magnetometers in key areas of biomagnetism. The first-generation sensors are designed to transition OPM technology from a physics laboratory to researchers in the medical community. The laser and optical components are tightly integrated inside the sensor package, and the sensor is tethered to a dedicated electronics signal processing unit that enables automated and standalone operation inside a magnetically shielded room.

In the pursuit of developing a portable wavelength reference, a photonically integrated chip (PIC) was developed to perform high resolution spectroscopy in a small package. The PIC outcouples light from one grating into free space where it is reflected and directed into an adjacent grating that couples into a separate waveguide. These gratings are extreme-mode-converters which convert the confined mode with a characteristic mode size of less than a micron to a collimated 100 micron diameter beam in order to mitigate transit time broadening for high resolution spectroscopy as well as reduce the diffraction angle. A miniature atomic vapor cell is inserted in the path of the beam to complete the spectroscopic platform. Preliminary results demonstrate sub-Doppler features. Coupling into the chip is achieved using fiber arrays enabling the spectroscopic signal to be routed back through an optical fiber and monitored. A laser is then locked to these sub-Doppler features completing an integrated wavelength reference. Analysis of the atom-light interactions made available by this platform will be discussed with an emphasis on the application of such structures to portable wavelength metrology.

Quantum technologies have been introduced widely in different scientific fields and some industry application have been developed. In this work we outline the history and development of a new field of Astronomy which is based on the concept of quantum mechanics and takes advantage from the technological instruments developed recently for quantum information in order to investigate new properties of the light coming from the sky. The development of this Quantum Astronomy instruments is still very active (e.g. Adaptive Optics integration) and the scientific target is pushed to new exiting limits: for example, periodic optical monitor of pulsars, lunar occultation; transit-occultations and application of the Hanbury Brown Twiss Intensity Interferometry.

We demonstrate a scheme for atom interferometry to measure multiple axes of accelerations and rotations based on a single-diode laser and a pyramidal magneto-optical trap. The atom interferometer is constructed based on a simple and robust design. Additionally, with zeroed AC Stark shift, efficient Raman transition has been achieved by use of modest laser intensity and a small single photon detuning. By irradiating Raman beams toward not only the whole pyramid but also individual pyramidal faces, multiaxis atom interferometers have been operated. As a demonstration, the vertical interferometer measures the gravity with a sensitivity of 6 μm/s² /√Hz and one interferometer along the diagonal axis observes the long-term tilt drift of the platform with a sensitivity of 4 μrad/√Hz. As a gyroscope, the atom interferometer along the diagonal axis achieves a sensitivity of 300 μrad/s/√Hz. This work paves the way toward compact, precise and multiaxis atom interferometers for geodesy, geology, or inertial navigation.

Atom interferometers consist of light pulses designed to create coherent superpositions of atomic states (“π/2” or “beam splitting” pulses) and that coherently interchange states (“π” or “mirror” pulses). In this article, we investigate the effects of imperfect pulses for a geometry specific to our apparatus. Atoms emerge from a 2-dimensional magneto-optical trap (2D MOT) in a continuous beam and cross continuous laser beams that drive stimulated Raman transitions. We use the atoms’ transit time through the laser field as the “pulse” time. We describe the impact of various effects on the contrast of the Rabi cycling, specifically the longitudinal velocity spread, the laser beam diameter and the spacing between the laser beams.

The present work for the first time reports on studies of properties of dynamically excited coherent population trapping (CPT) resonances in cells without buffer gas (both with and without anti-relaxation coating of their inner walls). Over the 0−3 kHz range of CPT resonance scanning frequencies, the discriminant curve slope was determined, as well as measured stability of atomic clocks. The work provides details of the experiments and analyses prospects of application of results for improvement of atomic clock stability. The work also discusses the newly discovered different character of CPT resonance shape evolution in cells with and without buffer gas.