Weaverpayne4734

We report nonlinear optical characterization of cm-long polycrystalline silicon (poly-Si) waveguides at telecom wavelengths. Laser post-processing of lithographically-patterned amorphous silicon deposited on silica-on-silicon substrates provides low-loss poly-Si waveguides with surface-tension-shaped boundaries. Achieving optical losses as low as 4 dB cm-1 enabled us to demonstrate effects of self-phase modulation (SPM) and two-photon absorption (TPA). Analysis of the spectral broadening and nonlinear losses with numerical modeling reveals the best fit values of the Kerr coefficient n2=4.5×10-18 m W-1 and TPA coefficient βTPA=9.0×10-12 m2 W-1, which are within the range reported for crystalline silicon. On-chip low-loss poly-Si paves the way for flexible integration of nonlinear components in multi-layered photonic systems.We investigated the use of backscatter properties of atmospheric ice particles for space-borne lidar applications. We estimated the average backscattering coefficient (β), backscatter color ratio (χ), and depolarization ratio (δ) for ice particles with a wide range of effective radii for five randomly oriented three-dimensional (3D) and three quasi-horizontally oriented two-dimensional (2D) types of ice particle using physical optics and geometrical integral equation methods. This is the first study to estimate the lidar backscattering properties of quasi-horizontally oriented non-pristine ice crystals. We found that the χ-δ relationship was useful for discriminating particle types using Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO) Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP) data. The lidar ratio (S)-δ relationship, which is determined using space-borne high-spectral-resolution lidar products such as EarthCARE ATLID or future space-borne lidar missions, may also produce robust classification of ice particle types because it is complementary to the χ-δ relationship.Electromagnetically induced transparency allows for the controllable change of absorption properties, which can be exploited in a number of applications including optical quantum memory. In this paper, we present a study of the electromagnetically induced transparency in a 167Er7LiYF4 crystal at low magnetic fields and ultra-low temperatures. The experimental measurement scheme employs an optical vector network analysis that provides high precision measurement of amplitude, phase and group delay and paves the way towards full on-chip integration of optical quantum memory setups. We found that sub-Kelvin temperatures are the necessary requirement for observing electromagnetically induced transparency in this crystal at low fields. A good agreement between theory and experiment is achieved by taking into account the phonon bottleneck effect.Resulting from strong magnetic anisotropy two-dimensional ferromagnetism was recently shown to be stabilized in chromium triiodide, CrI3, in the monolayer limit. While its properties remain largely unexplored, it provides a unique material-specific platform to unveil its electromagnetic properties associated with coupling of modes. Indeed, trigonal symmetry in the presence of out-of-plane magnetization results in a non-trivial structure of the conductivity tensor, including the off-diagonal terms. In this paper, we study the surface electromagnetic waves localized in a CrI3-based structure using the results of ab initio calculations for the CrI3 conductivity tensor. In particular, we provide an estimate for the critical angle corresponding to the surface plasmon polariton generation in the Kretschmann-Raether configuration by a detailed investigation of reflectance spectrum as well as the magnetic field distribution for different CrI3 layer thicknesses. We also study the bilayer structure formed by two CrI3 layers separated by a SiO2 spacer and show that the surface plasmon resonance can be achieved at the interface between CrI3 and air depending on the spacer thickness.We demonstrate a dual-comb spectrometer based on electro-optic modulation of a continuous-wave laser at 10 GHz. The system simultaneously offers fast acquisition speed and ultrabroad spectral coverage, spanning 120 THz across the near infrared. Our spectrometer is highly adaptable, and we demonstrate absorption spectroscopy of atmospheric gases and a dual-comb configuration that captures nonlinear Raman spectra of semiconductor materials via coherent anti-Stokes Raman scattering. selleckchem The ability to rapidly and simultaneously acquire broadband spectra with high frequency resolution and high sensitivity points to new possibilities for hyperspectral sensing in fields such as remote sensing, biological detection and imaging, and machine vision.Generating a prescribed irradiance distribution given a source distribution is an inverse problem that sits at the heart of illumination design. The growing prevalence of freeform optics has inspired several design methods for obtaining a prescribed irradiance distribution possessing no symmetry. Up to now, these methods have relied exclusively on freeform optical surfaces for generating freeform irradiances. This paper presents a design method that, for the first time, applies gradient-index (GRIN) optics to solving this inverse problem. Using a piecewise-continuous freeform gradient-index (F-GRIN) profile, a single optic with two planar surfaces can be designed to produce a far-field prescribed irradiance distribution from a point source. The design process is herein presented along with two design examples which demonstrate some of the unique properties of F-GRIN illumination optics.A receiver for weak frequency-coded microwave signal reception based on microring resonators array is proposed. This setup uses the nonlinear interaction of a microwave signal and an optical pump to generate an up-conversion signal to achieve the wideband signal reception. The minimum detectable power of this method reaches -93.2 dBm, which is suitable for the detection of weak signals. The results demonstrate a huge power conversion efficiency with η = 4.37×104, a wide conversion bandwidth of 2π×200 MHz, and a large 1-dB compressed dynamic range of 70.2 dB. The receiver can directly use the microwave signal received by the antenna that greatly reduces the volume and power consumption of the detection system. It is highly competitive in microwave photonics radar fields.