Michelsenwilkerson9561

Although imaging scatterometry has been demonstrated to be a powerful technique for characterization of nano-gratings when high lateral resolution is required, some limits of this novel technique are still undisclosed yet, such as the constraint for the imaging numerical aperture (NA), the number of unit cells for accurate grating reconstruction, and the analyzability of image pixels associated with the grating region. To this end, we establish a vectorial image formation (VIF) model for imaging scatterometry based on the finite-difference time-domain (FDTD) method and vectorial diffraction theory. According to the established VIF model and the simulation results of a Si grating sample with finite numbers of unit cells, we find that accurate grating reconstruction by routine RCWA (rigorous coupled-wave analysis) -based data analysis requires an upper limit for the NA of the employed objective. And enough numbers of unit cells are also required to be covered in the illumination spot. Only in these conditions, the zeroth-order diffraction information of the grating under test can be exclusively and completely collected by the imaging system. Moreover, only the image pixels off the edge of the grating region are analyzable by routine RCWA-based data analysis due to the effect of edge scattering. The required number of grating unit cells and the size of the analyzable region are closely related with the imaging NA and the ratio between the illumination spot size and the size of the grating region D/L. Higher imaging NA or smaller D/L typically requires fewer grating unit cells and meanwhile allows a larger analyzable region. The investigation in this paper promises to provide valuable insights into the application of imaging scatterometry.A significant enhancement of the longitudinal magneto-optical effect is demonstrated numerically and experimentally in transmission, and for small angles of incidence, through a subwavelength resonant structure consisting of a dielectric grating on top of a magneto-optical waveguide. The enhanced polarization rotation is associated with a high transmittance. These low footprint devices may thus be suitable for applications like magnetic field sensors or in non-destructive testing.A new scheme of three-frequency differential detection with a sideband locking technique is firstly proposed to suppress backscattering noise for improving the accuracy of resonator fiber optic gyroscope (RFOG). In the system we proposed, one light path is divided into three paths and sinusoidal wave modulations of different frequencies are respectively applied to generate the sideband. The first-order sidebands of the three channels of light in the cavity are locked to the adjacent three resonance peaks by sideband locking technique. The carrier and the remaining sidebands of the three channels of light are moved to a position away from the resonance peak, thereby achieving the purpose of being suppressed by the cavity itself. As a result, the frequency difference between the CW light and the other two CCW lights reaches one free spectral range (FSR), eliminating the expected backscattering noise. The experimental results demonstrate that the RFOG has a bias stability 0.9°/h based on the Allan deviation, and the corresponding angular random walk (ARW) 0.016°/√h, which validate that our scheme can effectively suppress backscattering noise to promote performance of RFOG in practical applications.We have developed a new method for selecting the test color sample set (TCSS) used to calculate CIE 2017 color fidelity index (CIE-Rf). Taking a Large Set as a starting point, a new optimized color sample set (OCSS) is obtained by clustering analysis. Taking metamerism phenomenon into account, spectra clustering is performed within the class obtained from color appearance attributes clustering. The CIE-Rf of 1202 light sources are calculated and analyzed by taking the Large Set, OCSS and CIE color evaluation sample set (CIE CESS-99) as TCSS. Through analyzing CIE-Rf, the performance of the OCSS is further investigated. Cobimetinib datasheet The results show that the clustering analysis method developed in this paper can be well used in selecting test color samples, and the obtained OCSS can represent Large Set well and be better used for color fidelity metrics of light sources.We report on the excitation and polarization preserved propagation of a very large effective-area (Aeff ∼ 2240 μm2) higher-order-mode in an optical fiber. A laser signal operating in the 1 μm wavelength region is transported in a Bessel-like LP0,4 mode over a 10 m long section of the polarization-maintaining higher-order-mode fiber. We observe that the light propagates through the fiber with >10 dB polarization-extinction-ratio as the fiber is coiled into circular loops of 40 cm diameter.We present an on-chip, widefield fluorescence microscope, which consists of a diffuser placed a few millimeters away from a traditional image sensor. The diffuser replaces the optics of a microscope, resulting in a compact and easy-to-assemble system with a practical working distance of over 1.5 mm. Furthermore, the diffuser encodes volumetric information, enabling refocusability in post-processing and three-dimensional (3D) imaging of sparse samples from a single acquisition. Reconstruction of images from the raw data requires a precise model of the system, so we introduce a practical calibration scheme and a physics-based forward model to efficiently account for the spatially-varying point spread function (PSF). To improve performance in low-light, we propose a random microlens diffuser, which consists of many small lenslets randomly placed on the mask surface and yields PSFs that are robust to noise. We build an experimental prototype and demonstrate our system on both planar and 3D samples.Properly designed black phosphorus (BP) ribbons exhibit extreme anisotropic properties, which can be used to fabricate a high-efficiency transmitter or reflector depending on the linear polarization of excitation. In this study, we design a highly efficient and broad-angle polarization beam splitter (PBS) based on extremely anisotropic BP ribbons around the mid-infrared frequency region with an ultra-thin structure, and study its performance by using transfer matrix calculation and finite element simulation. In the broad frequency range of 80.4 terahertz - 85.0 terahertz (THz) and an wide angle range of more than 50°, the reflectivity and transmissivity of the designed PBS are both larger than 80% and the polarization extinction ratios are higher than 25.50 dB for s-polarization light and 20.40 dB for p- polarization light, respectively. Furthermore, the effect of incident angle and device parameters on the behavior of the proposed PBS is examined. Finally, we show that the operation frequency of this PBS can be tuned by the electron concentration of BP, which can facilitate some practical applications such as tunable polarization splitters or filters, and mid-infrared sensors.A multi-scale direct writing method for metal microstructures is proposed and demonstrated. In this study, metal structures were created in a gelatin matrix containing silver nitrate by photoreduction using a 405-nm blue laser. The influence of concentrations of materials in the sample solution was evaluated by measuring the conductivity of the fabricated microstructures. The fabrication line width could be controlled by changing the laser scanning speed. A network structure was also observed, which possibly helps in increasing the microstructure's conductivity. Finally, we demonstrated multi-scale drawing by using objective lenses with different numerical apertures. Our method can result in new possibilities for conductive metal direct writing.A photonics-based anti-chromatic dispersion transmission scheme for multi-band linearly frequency modulated (LFM) signals is proposed and experimentally demonstrated. In the central station (CS), the key component is an integrated dual-polarization quadrature phase shift keying (DP-QPSK) modulator, of which the up-arm and down-arm are driven by a microwave reference signal and an intermediate-frequency (IF) LFM signal respectively. By properly adjusting the DP-QPSK modulator, optical frequency comb (OFC) and frequency shift lightwave are generated. After polarization coupling and remote transmission, the orthogonal-polarization optical signals are introduced into balanced photodetector for heterodyne detection. Thence, multi-band LFM signals are generated and transmitted to remote base stations (BS) with the largest power for the anti-chromatic dispersion ability. Experiments are conducted to verify the analysis. Multi-band LFM signals at L (1.5 GHz), C (7 GHz), X (10 GHz), Ku (15.5 GHz) and K (18.5 GHz) bands with flatness of 1.9 dB are simultaneously obtained in the CS after 50 km fiber transmission, while the normally double-sideband modulation approach experiences a significant power fading for the fiber dispersion. Tunability of the system is evaluated, and detection performances of the generated signals are also analyzed.Active spectral tuning of nanophotonic devices offers many fascinating prospects for the realization of novel optical function. Here, switchable spectral response is enabled by the architecture of one-dimensional (1D) photonic crystal (PC) integrated with phase change material of the germanium antimony telluride (GST). Active and precise tuning of the bistable passband and central resonant frequency is demonstrated in the 1D PC composed of alternate SiN and GST nanofilms. An analytical model is derived to specify the tunable spectral features, including the band gap and resonant frequencies. Both the measured and calculated results show distinct red shifts of passband and the resonant minima (or maxima), well confirming theoretical predictions. This work demonstrates a route to construct active photonic devices with the electrically or thermally tunable spectra via 1D PC and potentially extends diverse applications based on the PC platform.The photo-excited electrons and holes move in the same direction in the diffusion and in the opposite direction in the drift under an electric field. Therefore, the contribution to the inverse spin Hall current of photo-excited electrons and holes in the diffusion regime is different to that in the drift regime under electric field. By comparing the classical Hall effect with the inverse spin Hall effect in both diffusion and drift regime, we develop an optical method to distinguish the contributions of electrons and holes in the inverse spin Hall effect. It is found that the contribution of the inverse spin Hall effect of electrons and holes in an InGaAs/AlGaAs un-doped multiple quantum well is approximately equal at room temperature.Optical nanofiber is a widely adopted platform for highly efficient light-matter interaction by virtue of its exposed evanescent field with high light intensity. However, the strongly constrained mode field with the wavelength-scale size makes the light-matter interaction time limited in consideration of the random thermal motion of warm molecules, which results in considerable transit-time dephasing and thus line broadening. Here we report a systematic study of the transit-time effect associated with the optical nanofibers. Both simulation and experiment for nanofibers exposed in acetylene demonstrate the considerable transit-time broadened linewidth in the low-pressure range.