Zobrazení zdroje stránky Floresgates9315

The referenced article [Appl. Opt.59, 11112 (2020)APOPAI0003-693510.1364/AO.412267] has been retracted by the author.A comparator is one of the important combinational logic circuits. An optical comparator was designed and simulated based on photonic crystals. Point and linear defects were also used in the proposed optical comparator. The use of simple defect paths and the absence of ring resonators reduced the complexity of the structure. One of the characteristics of the proposed structure is that it has a very small size, which leads to the suitability of this comparator for optical integrated circuits. [https://www.selleckchem.com/products/pf-06650833.html https://www.selleckchem.com/products/pf-06650833.html] Another characteristic of this comparator is an increase in the optical power difference for the logical values "0" and "1," which reduces the bit detection error in the output. This comparator is also designed to operate on the 1.55 µm wavelength, and it can be used in today's optical telecommunication circuits.A Laguerre-Gaussian (LG) vortex beam is employed as an illumination source for a dark-field microscopy imaging system. To discover the influences of beam characteristics on the imaging quality, an analysis model has been established to show the light-field change rule on both object and image planes. The analytic expressions of the light field on the two planes are deduced. When a rectangular defect is simulated, the light distributions on the object and image planes with different parameters are calculated. The results show that the size of the beam spot on the object plane can be changed by adjusting the topological charge of the vortex beam to obtain the best imaging effect for defects of different scales.We report a study of the response function parameters (amplitude and rise/fall time) of a high-speed GaSb/GaInAsSb/GaAlAsSb photodiode operating at 1.9 µm as a function of optical input power and reverse bias voltage. The experimental measurement results yield the optimal pulse energy and optimal reverse bias voltage for the photodiode. The 44 ps minimal rise time of the response function and 3.6 GHz bandwidth are achieved under a 3 V reverse bias voltage and pulse energy in the 0.27-2.5 pJ range.We present low-loss microscope optics using an axicon-based beam shaper, which can convert a Gaussian beam to a ring beam to minimize the optical loss from blocking by the back aperture of the objective lens while maintaining spatial resolution. To design the beam shaper, we characterize the position-dependent transmittance of high-transmittance objective lenses and numerically calculate the beam propagation in the beam shaper. We also clarify the effect of misalignments of the beam shaper and wavefront distortion of the input beam. Furthermore, we experimentally demonstrate a low-loss microscope optical system with a high transmittance of 86.6% and high spatial resolution using the full numerical aperture of the objective lenses.Studying the aero-optical effects induced by turbulent structures with different scales helps determine the capture scale of turbulent structures in experiments/calculations and improve the turbulence breakup device. In this paper, the density field of a supersonic turbulent boundary layer at Ma=3.0 was measured based on the nano-tracer plane laser scattering technique. Two-dimensional orthogonal wavelet multi-resolution analysis was applied to obtain information about different flow scales. The ray-tracing method simulates the propagation of a Gaussian plane beam through the nonuniform flow field at different resolutions. The results show that the turbulent boundary layer thickness and its calculation method lead to the difference in scaling calculation results among the existing experiments. The turbulent structures about 0.7δ contribute most to aero-optical effects. With the reduction of the resolution, the contribution of small turbulent structures to aero-optical effects reduces obviously. When the minimum scale of turbulent structures captured is larger than 0.072δ, the resolution can no longer reflect the real aero-optics results of turbulent structures. The smallest optically active scale predicted is 0.017δ in Mani's theory. The turbulent structures smaller than 0.018δ have little effect on optical path difference (OPD), and the higher-order quantities change significantly around 0.009δ∼0.018δ. According to experimental results, it is promising to improve the aero-optical suppression effects by breaking the large eddy into the turbulent structures smaller than 0.018δ, or even 0.009δ.A dual-band terahertz metamaterial narrowband absorber is investigated based on a single simple windmill-shaped structure. The proposed metamaterial absorber achieves near-perfect absorption at 0.371 THz and 0.464 THz. The full width at half-maximum is 0.76% and 0.31% relative to absorption frequency. The multireflection interference theory is used for analyzing the absorption mechanism at low absorption frequency. The theoretical predictions of the decoupled model have excellent agreement with simulation results. By investigating the absorber's distribution of electric field and surface current density at high absorption frequency, the absorber's near-perfect absorption at the high absorption frequency originating from the magnetic resonance formed between the top metal structure and the bottom metal plane is explained. Besides, the absorber proposed is independent of the polarization angle. It is significant to various applications such as narrowband thermal radiation, photoelectric detection, biological sensing, and other fields.The precise alignment of the space telescope with an active secondary mirror (ASM) is essential to high-quality imaging. The traditional alignment methods either require a dedicated wavefront sensor or a lot of iterations to optimize a metric function, which is not suitable for on-orbit instant alignment. A model-based wavefront sensorless adaptive optics method is proposed for the alignment of the ASM of a wide field-of-view space telescope. In our method, the aberration is estimated by introducing a series of modal biases successively into the system using the ASM. Unlike the traditional wavefront sensing methods that intend to measure all aberration modes, only five aberration modes that can be compensated by the ASM are estimated. Two alignment schemes either using single-field or multi-field images are proposed to calculate the control signals of the ASM, depending on if the aberration is mainly caused by the ASM. Simulations are made to evaluate the performance of our method under different scenarios. The influence of image sampling frequency, image size, and image noise on alignment are also investigated.