Precise spatial characterization of vectorial beams is crucial for many advanced optical experiments, but challenging when wavefront and polarization features are involved together. Here we propose a reference-free method aimed at extracting the map of the complex-amplitude components of any coherent beam at an optical-microscopy resolution. Our method exploits recent advances in ptychographic imaging approaches. We emphasize its versatility by reconstructing successfully various experimental vectorial beams including polarization and phase vortices, the exit field of a multicore fiber and a speckle pattern.Controlling the polarization state of an optical pulse within a short gating time facilitates ultrafast all-optical data processing and recording. Using the innovative all-optical modulation method such as the transient terahertz Kerr effect (TKE), the polarization state of the optical pulse can be switched within the gating time on the sub-picosecond scale. In this work, we use high-frequency single-cycle terahertz (THz) pulses to excite the Kerr effects of materials and explore the potential to shorten the gating time of the polarization modulator. https://www.selleckchem.com/products/Vorinostat-saha.html A low-density polyethylene (LDPE) material with good Kerr-related properties is proposed to improve the performance of the TKE-based modulator and the obtained ultrafast gating time (FWHM) can reach 86 fs. Experimental evidence for the thickness dependence of the Kerr response demonstrates that the errors caused by optical transmission factors in the LDPE medium can be ignored, and thus the ultrafast gating modulation is mainly limited by the duration of probe pulse. Compared with common TKE-based materials, we believe that the low-cost LDPE is a good candidate to achieve high-power TKE-based ultrafast pulse switching.In this paper, we demonstrate a novel approach utilizing tunnel junction (TJ) to realize GaN-based distributed feedback (DFB) laser diodes (LDs). Thanks to the use of the TJ the top metal contact is moved to the side of the ridge and the DFB grating is placed directly on top of the ridge. The high refractive index contrast between air and GaN, together with the high overlap of optical mode with the grating, provides a high coupling coefficient. The demonstrated DFB LD operates at λ=450.15 nm with a side mode suppression ratio higher than 35dB. The results are compared to a standard Fabry-Perot LD.We propose a realistic physical scheme to realize linear Gaussian optical potential with parity-time (PT) symmetry and two dimensional (2D) spacial solitons in a coherent atomic gas. It is shown that the PT-symmetric potential can be created through the spatial modulation of the control and relevant atomic parameters. We find that the Gaussian PT potential parameters, the imaginary part and the width and the position, play crucial roles in the occurrence of the PT phase transition. We demonstrate that the system supports stable 2D dipole solitons and vortex solitons, which can be managed via tuning PT potential. Furthermore, the dynamic characteristics of the symmetric scatter and collision of solitons are shown.Perfect optical absorption occurs in a metasurface that supports two degenerate and critically-coupled modes of opposite symmetry. The challenge in designing a perfectly absorbing metasurface for a desired wavelength and material stems from the fact that satisfying these conditions requires multi-dimensional optimization often with parameters affecting optical resonances in non-trivial ways. This problem comes to the fore in semiconductor metasurfaces operating near the bandgap wavelength, where intrinsic material absorption varies significantly. Here we devise and demonstrate a systematic process by which one can achieve perfect absorption in GaAs metasurfaces for a desired wavelength at different levels of intrinsic material absorption, eliminating the need for trial and error in the design process. Using this method, we show that perfect absorption can be achieved not only at wavelengths where GaAs exhibits high absorption, but also at wavelengths near the bandgap edge. In this region, absorption is enhanced by over one order of magnitude compared a layer of unstructured GaAs of the same thickness.In the Raman probing of multilayer thin film materials, the intensity of the measured Raman scattered light will be impacted by the thickness of the thin film layers. The Raman signal intensity will vary non-monotonically with thickness due to interference from the multiple reflections of both the incident laser light and the Raman scattered light of thin film interfaces. Here, a method for calculating the Raman signal intensity from a multilayer thin film system based on the transfer matrix method with a rigorous treatment of the Raman signal generation (discontinuity) is presented. This calculation methodology is valid for any thin film stack with an arbitrary number of layers with arbitrary thicknesses. This approach is applied to several thin film material systems, including silicon-on-sapphire thin films, graphene on Si with a SiO2 capping layer, and multilayer MoS2 with the presence of a gap between layers and substrate. Different applications where this method can be used in the Raman probing of thin film material properties are discussed.In this paper, a high-sensitivity optical fiber temperature sensor based on a dual-loop optoelectronic oscillator (OEO) with the Vernier effect has been proposed and experimentally demonstrated. Different from the traditional dual-loop OEOs which comprise a very long loop and a short loop to achieve low-phase noise and single-mode selection, the proposed OEO scheme has two loops with slightly different lengths and does not use any RF filters. A part of the fiber in one of the loops is used as a temperature sensing element as well as the delaying component. An obvious Vernier effect has been generated in the frequency response of the OEO. By detecting the frequency shift of the envelope peak of the measured frequency response curve, the temperature sensing interrogation of the dual-loop OEO based sensor is conducted. The experimental results show that the sensitivity of the proposed dual-loop OEO based temperature sensor can be improved from 6.625 KHz/°C for a single-loop OEO to 210.25KHz/°C by employing the Vernier effect.