Yuri S. Kivshar

Scattering of the discrete solitons on the

We study the propagation of linear waves and solitons in an array of optical waveguides with an embedded defect created by a pair of waveguides with gain and loss satisfying the so-called parity-time () symmetry condition. We demonstrate that in the case of small soliton amplitudes, the linear theory describes the scattering of solitons with a good accuracy. We find that the incident high-amplitude solitons can excite the mode localized at the -symmetric defect. We also show that by exciting the localized mode of a large amplitude, it is possible to perform phase-sensitive control of soliton scattering and amplification or damping of the localized mode.

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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.

-symmetric defects

The resonant high-index nanostructures open opportunities for control many optical effects via optically-induced electric and magnetic Mie resonances, mostly localized inside the structures. Especial interest such nanostructures represent for quantum emitters placed inside, that makes possible enhancement of quantum source emission through resonant coupling to localized modes. We have proposed the concept of active dielectric nanoantennas based on nanodiamonds with embedded NV-centers. The study of theoretically dependence of optical properties of this system on the spectral position of the resonant modes has demonstrated that that at some sizes of the diamond spherical particles and certain position of the dipole in the sphere the Purcell factor can achieve the value of 30. We have demonstrated experimentally that the photoluminescence properties of the NV-centers can be controlled via scattering resonances and observed a decrease of the NV-centers lifetime in the studied diamond particles, as compared to nonresonant nanodiamonds. These results are in a good agreement with our theoretical calculations for the average Purcell factor for multiple NV-centers within a nanoparticle. The simplicity of the proposed concept compared to existing photonic cavity systems and applicability for a wide range of color centers in diamond make active diamond nanoantenna an effective tool for creating controllable emitting elements in the visible range for future nanophotonic devices.

Polychromatic Multigap Solitons in Nonlinear Photonic Lattices

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.

Control of the NV-centers fluorescence lifetime in resonant diamond particles (Conference Presentation)

Optical nanoantennas possess great potential for controlling the spatial distribution of light in the linear regime as well as for frequency conversion of the incoming light in the nonlinear regime. However, the usually used plasmonic nanostructures are highly restricted by Ohmic losses and heat resistance. Dielectric nanoparticles like silicon and germanium can overcome these constrains [1,2], however second harmonic signal cannot be generated in these materials due to their centrosymmetric nature. GaAs-based III-V semiconductors, with non-centrosymmetric crystallinity, can produce second harmonic generation (SHG) [3]. Unfortunately, generating and studying SHG by AlGaAs nanocrystals in both backward and forward directions is very challenging due to difficulties to fabricate III-V semiconductors on low-refractive index substrate, like glass. Here, for the first time to our knowledge, we designed and fabricated AlGaAs nanoantennas on a glass substrate. This novel design allows the excitation, control and detection of backwards and forwards SHG nonlinear signals. Different complex spatial distribution in the SHG signal, including radial and azimuthal polarization originated from the excitation of electric and magnetic multipoles were observed. We have demonstrated an unprecedented SHG conversion efficiency of 10-4; a breakthrough that can open new opportunities for enhancing the performance of light emission and sensing [4]. References [1] A. S. Shorokhov et al. Nano Letters 16, 4857 (2016). [2] G. Grinblat et al. Nano Letters 16, 4635 (2016). [3] S. Liu et al. Nano Letters 16, 7191 (2016). [4] R. Camacho et al. Nano Lett. 16, 7191 (2016).

All-dielectric metasurfaces for measuring multi-photon quantum-polarization states (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.

Directional second harmonic generation from AlGaAs nanoantennas (Conference Presentation)

In this invited talk I will review our research activity on near-field Anapole nanolasers. Anapoles are radiationless light states that do not possess far field emission. Thanks to their unique nature, these states enable a new concept of laser source, whose emission is totally confined in the near field. We will discuss applications of this concept for ultra-fast (100 fs), mode-locking pulse generation in integrated optical structures with GaAs semiconductors.

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

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.

Anapole-mode-based nanolaser in integrated optical chips (Conference Presentation)

We review our recent theoretical and experimental results in different types of microwave metamaterials and backward-wave structures, including nonlinear transmission lines, two-dimensional cut-wire structures, and nonlinear split-ring resonator metamaterials.

High Effciency Harmonic Generation in LiNbO 3 Membranes

We present experimental and theoretical study of refractive index modification induced by femtosecond laser pulses in photorefractive crystals. The single pulses with central wavelength of 800 nm, pulse duration of 150 fs, and energy in the range of 6-130 nJ, tightly focused into the bulk of Fe-doped LiNbO3 and stoichiometric LiTaO3 crystals induce refractive index change of up to about 10-3 within the volume of about (2.0 x 2.0 x 8.0) μm3. The photomodification is independent of the polarization orientation with respect to the crystalline c-axis. The recorded region can be erased optically by a defocused low-intensity single pulse of the same laser. Recording and erasure can be repeated at the same position many times without loss of quality. These findings demonstrate the basic functionality of the ultrafast three-dimensional all-optical rewritable memory. Theoretically they are interpreted by taking into account electron photogeneration and recombination as well as formation of a space-charge field. The presented analysis indicates dominant role of photovoltaic effect for our experimental conditions, and suggests methods for controlling various parameters of the photomodified regions.