查看更多>>摘要：The influence of the spatiotemporal coherence of the broadband laser on beam smoothing of the induced spatial incoherence (ISI) was analyzed. In such a scheme of ISI combined with lens array (LA) and polarization control plate (PCP), the broadband laser with spatiotemporal decoherence is adopted as the laser source, while ISI and PCP are employed to introduce spatial incoherence to the beamlets. Simulation results indicate that, the temporal decoherence arising from the broadband spectrum combining with the spatial decoherence induced by ISI and PCP brings about the ultrafast intensity variation of the focused spot and the spatial decoherence due to the application of partial coherent beam (PCB) mitigates the hard-edged diffraction effect of sub-beams arising from LA. As a result, the irradiation uniformity of the integral focused spot is significantly improved with a reduced time delay introduced to the pulse shape compared with the conventional ISI scheme. Besides, the requirement of the spatiotemporal decoherence can be further relaxed by optimizing the distance between the focal plane and the target plane, as well as the number of element lenses in LA.
查看更多>>摘要：Huygens' metasurface (HMS) can realize high-efficient real-time control of electromagnetic waves through impedance matching,which is specialty of multipoles. Previous designs of HMS mostly focus on realizing 27r phase coverage by combining different poles, while ignoring the limitation on transmittance caused by different attributes between poles. In this paper, we propose a new design of HMS, which can fulfill the excitation of the pure magnetic quadrupole (MQ) on target wavelength. Combined with the theory of multipole scattering, we strip off the interference of electric quadrupole by adding glass layers to the cross-shaped units. By optimizing the parameters of the unit after adding glass, we get an HMS element with extremely high transmittance and phase distribution covering full 27r. We found that the peak of MQ will be simultaneously affected by the thickness and position of glass, while the peak position will only be affected by the former. We also characterize the wavefront manipulation performance of the element by designing and simulating typical applications such as beam deflection, focusing and hologram reconstruction. This efficient wavefront modification indicates that multipole analysis is an effective way of dielectric Huygens' metasurface parameter optimization and can be applied to computer-generated holograms, structured color display devices.
查看更多>>摘要：In this article, an optical interconnection system from low temperature (4 K) to room temperature was built based on a conventional Distributed Feedback Laser. The curves of P-I-V and the spectra of Distributed Feedback Laser were characterized from 296K to 4K. The laser spectrum had a significant blue shift from 296 K to 4 K, the bandwidth of 16.18 GHz and 12 Gbps eye diagram was achieved.
查看更多>>摘要：Conventional methods for three-dimensional (3D) imaging frequently rely on voxel-by-voxel data acquisition, which restricts the range of specimens in which they can be effectively employed. While advances in imaging technology now permit the routine acquisition of 3D images approaching video rates, there are other limitations to image formation in fluorescent microscopy that prohibit studies in large volume samples, highly scattering media, and dynamic environments. Some approaches to 3D image collection circumvent this need by the use of tomographic imaging, where sub-3D projections are collected at varying illumination angles and reconstructed through an inversion algorithm to compute an estimate of the 3D fluorophore distribution. Many such methods rely on spatially coherent light, and thus prohibit the use of fluorescent light. By employing unique spatiotemporally varying illumination patterns in conjunction with computational imaging approaches to image reconstruction, we show that some limitations of laser scanning and wide-field imaging can be overcome. We outline several approaches that utilize tomographic projections with patterned illumination to collect 3D image data. All three dimensional optical imaging exploits projection of the desired 3D information into a lower-dimensional subspace, and then a full three dimensional object is estimated from these data. We discuss a number of such single pixel strategies that project object information onto a zero-dimensional, usually a power, measurement. Further, we outline computational image reconstruction approaches that enhance the object estimates by employing a forward model for the image formation process.
Kim, JunwooHwang, Won SangKim, DongeunKim, Dug Young...
8页
查看更多>>摘要：By using the microscopic Beer-Lambert law (MBL), we propose a fast and effective analysis method for retrieving the absorption coefficient changes of a sample from broadband frequency-domain diffuse optical spectroscopy (FD-DOS) or frequency-domain near-infrared spectroscopy (FD-NIRS) data. To verify the advantages of our proposed method, we built a broadband frequency-domain single-distance diffuse optical imaging (DOI) system for measuring the amplitude and the phase of transmitted light. Fifteen liquid phantoms with different absorption and scattering coefficients are prepared, and the changes in the absorption coefficient delta mu(s) are retrieved by using the conventional nonlinear least-squares fitting (NLSF) and the proposed MBL methods. Results show that the computation time and the precision of the MBL method are much better than those of the NLSF method, respectively.
查看更多>>摘要：Localized optical resonances in silicon nanostructures have been increasingly used in color printing. By changing the geometric parameters of the silicon nanostructures to obtain different structural colors, it is possible to get a larger coverage range than the sRGB color gamut in the CIE color space, and achieve ultra-high-resolution color printing. However, the design of specific colors involves iterative optimization of geometric parameters, which is computationally expensive. Thus, it is very challenging to obtain millions of different colors in the color space. In this paper, we trained a feature-crossed neural network with attention mechanism to predict the structural color produced by random silicon nano truncated cones with high accuracy. On the problem of inverse design, we improve the loss function of the tandem network, which solves the non-uniqueness problem in the inverse design process and avoids the tandem net from falling into the wrong solution space. Our model can accurately predict millions of different color points in the CIE color gamut. In addition, the proposed methods can be easily extended to solve the optimization design problems in the field of nanophotonics.
查看更多>>摘要：Asymmetry error from the optical devices fabrication error is one of the main factors influencing the performance of resonant optical gyroscope (ROG). Research on the compensation of asymmetry error is meaningful to improve the performance of ROG. We theoretically analyze the difference of first harmonic demodulation curves in two loops and propose an effective method to compensate the asymmetry error via second harmonic demodulation curves. The experimental results show that, with our method, the bias stability of the gyroscope output is greatly reduced from 186 degrees/h to 9 degrees/h.
查看更多>>摘要：A multichannel plasmonic switch consisted of four metal-insulator-metal (MIM) waveguides and an equilateral triangle resonator (ETR) with a silver bar is proposed. Calculated by coupled mode theory (CMT) and standing wave theory, structural transmittance characteristics are numerically studied by finite difference time domain (FDTD) method. And the results show that the transmission spectrum of the ETR with a silver bar, coupled with a MIM waveguide, can be adjusted by increasing the height and width of the bar. As for the switch, varying with structural parameters of the bar, the transmission spectra in three ports can be tuned by rotating the bar into different angles. And this multichannel plasmonic switch owes a high on/off contrast ratio (R = 36 dB). The proposed switch has potential application value in the area of telecommunication and all-optical signal procession.
查看更多>>摘要：Inverse design through topology and dimension optimization can significantly improve the performance of metasurfaces as compared to the traditional point-by-point designs. However, it is very challenging to optimize large-area 3D gradient metasurfaces due to heavy electromagnetic simulation and slow converging speed. In this work, we propose a quick and efficient design approach of 3D large-area high-NA metalenses by simple rotation and translation of the 2D cylindrical lens, where the later can be optimized using basic searching algorithms. The simulation and experimental results together show the effectiveness of this approach, which has great potential to be generalized for fast optimization of other types of wavefront shaping metasurfaces with spatial symmetry.
查看更多>>摘要：We present a framework for computational ghost imaging based on deep learning and customized pink noise speckle patterns. The deep neural network in this work, which can learn the sensing model and enhance image reconstruction quality, is trained merely by simulation. The conventional computational ghost imaging results, deep learning-based ghost imaging results with white and pink noise are compared under multiple sampling ratios at different noise conditions. The experiments are done with digits, English letters, and Chinese characters. We show that the proposed scheme can provide high-quality images with a sampling ratio as low as 0.8% even when the object is outside the training dataset and robust to noisy environments. The method can be applied to a wide range of applications, including those requiring a low sampling ratio, fast reconstruction, or experiencing strong noise interference.
NSTL
Elsevier