Andrey A. Sukhorukov

Nonlinear reflection of optical beams in the media with a thermal nonlinearity

The features of the reflection of optical beams in the media with a defocusing thermal nonlinearity are analyzed. The dependence of the angle of the nonlinear total reflection on the power of the pump wave and the initial distance between the beams is determined. The reflection effects are studied for the interaction of the green (24 mW) and red (0.7 mW) laser beams that intersect at a relatively small angle (about 0.01 rad) in a 5-cm-long cuvette with the stained alcohol. The theoretical results are in good agreement with the experimental data.

Polychromatic Multigap Solitons in Nonlinear Photonic Lattices

We predict simultaneous self-trapping of multiple frequency beams in spectral gaps of periodic lattices, and demonstrate strong sensitivity of localization and mobility of such polychromatic multigap solitons on their spectra due to lattice-enhanced dispersion.

All-dielectric metasurfaces for measuring multi-photon quantum-polarization states (Conference Presentation)

With recent advances in nanophotonics, metasurfaces based on nano-resonators have facilitated novel types of optical devices. In particular, the interplay between different degrees of freedom, involving polarization and spatial modes, boosted classical polarization measurements and imaging applications. However, the use of metasurfaces for measuring the quantum states of light remains largely unexplored. Conventionally, the task of quantum state tomography is realized with several bulk optical elements, which need to be reconfigured multiple times. Such setups can suffer from decoherence, and there is a fundamental and practical interest in developing integrated solutions for measurement of multi-photon quantum states. We present a new concept and the first experimental realization of all-dielectric metasurfaces with no tuneable elements for imaging-based reconstruction of the full quantum state of entangled photons. Most prominently, we implement multi-photon interferometric measurements on a sub-wavelength thin optical element, which delivers ultimate miniaturization and extremely high robustness. Specifically, we realize a highly transparent all-dielectric metasurface, which spatially splits different components of quantum-polarization states. Then, a simple one-shot measurement of correlations with polarization-insensitive on-off click detectors enables complete reconstruction of multi-photon density matrices with high precision. In our experiment, we prepare sets of polarization states and reconstruct their density matrices with a high fidelity of over 99% for single photon states and above 95% for two-photon states. Our work provides a fundamental advance in the imaging of quantum states, where multi-photon quantum interference takes place at sub-wavelength scale.

Manipulation and measurement of optical coherence in PT photonic structures (Conference Presentation)

Optical coherence is of fundamental importance for both classical and quantum applications. This motivates the development of approaches for increasing the degree of coherence, which can be quantified by a measure of purity. The purity is preserved in linear conservative systems, and accordingly the manipulation of coherence was realized with specially introduced loss in bulk optical setups or diffraction on metal films involving optical absorption and plasmon coupling. Here we suggest and show experimentally for the first time that manipulation and measurement of optical coherence and state purification can be efficiently realized in integrated non-Hermitian parity-time (PT) symmetric photonic structures composed of elements with different loss or gain. Specifically, we design and fabricate laser-written waveguide directional couplers that contain two sections. The first section realizes a PT-like coupler, where one of the two waveguides features extra radiative losses via modulation. The second section consists of straight coupled waveguides with specially detuned propagation constants, which are optimized to enable a full reconstruction of the purity and optical coherence by measuring the interference pattern in both waveguides through fluorescence imaging. In PT symmetric regime, we observe that the purity of an initially fully incoherent (mixed) state is increased followed by a revival of the input state. This constitutes an important experimental evidence of reversible manipulation of light coherence in PT coupled waveguides. We anticipate that this method can facilitate a wide range of applications from classical to quantum optics, including filtering out noise and optimizing the visibility of interferometric measurements.

All-dielectric transparent metasurfaces for holography and quantum tomography (Conference Presentation)

Metasurfaces are ultra-thin patterned photonic structures that emerged recently as planar metadevices capable of reshaping and controlling incident light. They are composed of resonant subwavelength elements distributed across a flat surface. Due to the resonant scattering, each element can alter the phase, amplitude and polarization of the incoming light. Many designs and functionalities of metasurfaces suggested so far are based on plasmonic planar structures, however most of these metasurfaces demonstrate low efficiencies in transmission due to losses in their metallic components. In contrast, all-dielectric resonant nanophotonic structures avoid absorption losses, and can drastically enhance the overall efficiency, especially in the transmission regime. Here we utilize this platform to create flat optical elements such as vector beam q-plates, holograms and quantum polarization tomography devices. Holograms, in particular, showcase a potential of the metasurface platform as they rely on a complex wavefront engineering. Metasurface platform enables a new way to create highly efficient holograms with single-step patterning. Here, we design and realize experimentally greyscale meta-holograms with superior transmission properties. Another promising area for implementation of all-dielectric metasurfaces is quantum optics. We suggest and develop experimentally a new concept of quantum-polarization measurements with a single all-dielectric resonant metasurface. A metasurface enables full reconstruction of the state of entangled photon pairs based on the photon correlations with single-photon detectors. The subwavelength thin structure provides an ultimate miniaturization, scalability to a larger number of entangled photons, and gives the possibility to study the dynamics of quantum states in real-time.

High Effciency Harmonic Generation in LiNbO 3 Membranes

We reveal simultaneous phase- and group-velocity matching for frequency doubling of ultra-short pulses at telecom wavelengths in LiNbO3membranes. Furthermore, we predict complete phase-matched cascaded third-harmonic generation for optimized membrane thickness.

Observation Of Discrete Reflectionless Potentials

We observe experimentally discrete reflectionless potentials, which fully transmit all incident waves. This is realized in optical waveguide arrays, where the coupling is locally modulated according to a special transformation of Ablowitz-Ladik soliton profiles.

Nonlinear Diffusion and Self-Trapping of Light in Diffraction-Managed Photonic Lattices

We study nonlinear propagation of light in diffraction-managed photonic lattices created with periodically-curved arrays of optical waveguides. We identify a novel regime of nonlinear light diffusion in self-collimating structures where linear diffraction is suppressed.

Slow-Light Diffraction Management and Nonlinear Localization in Coupled Bragg-Grating Waveguides

We show that in specially designed nonlinear waveguides with phase-shifted Bragg gratings it is possible to realize the frequency-independent spatial diffraction in the vicinity of band-gap, allowing for efficient spatio-temporal self-trapping of slow-light pulses.

Gap solitons and mutual focusing in nonlinear periodic structures

We realized experimentally fully-controlled generation of gap and lattice soliton in nonlinear periodic structures. We demonstrated their unique features including incoherent interaction of solitons from different band gaps and the formation of stationary multi-gap solitons.