Reyesfox4937

Single-pixel imaging allows for high-speed imaging, miniaturization of optical systems, and imaging over a broad wavelength range, which is difficult by conventional imaging sensors, such as pixel arrays. However, a challenge in single-pixel imaging is low image quality in the presence of undersampling. Deep learning is an effective method for solving this challenge; however, a large amount of memory is required for the internal parameters. In this study, we propose single-pixel imaging based on a recurrent neural network. The proposed approach succeeds in reducing the internal parameters, reconstructing images with higher quality, and showing robustness to noise.Ultra-smooth surfaces with low contamination and little damage are a great challenge for aluminum optical fabrication. Ion beam sputtering (IBS) has obvious advantages of low contamination and non-contact that make it a perfect method for processing aluminum optics. However, the evolution laws of aluminum surface morphology are quite different from conventional amorphous materials, which affects the roughness change and needs systematic research. Thus, in this paper, the roughness evolution of an aluminum optical surface (i.e., aluminum mirror) subjected to IBS has been studied with experimental and theoretical methods. The surface morphology evolution mechanisms of turning marks and second phase during IBS are revealed. The newly emerging relief morphology and its evolution mechanism are studied in depth. The experimental results find that IBS causes the coarsening of optical surfaces and the appearance of microstructures, leading to the surface quality deterioration. Turning marks have been through the process of deepening and vanish, while second phase generates microstructures on the original surface. The corresponding mechanism is discussed exhaustively. Preferential sputtering, curvature-dependent sputtering and material properties play important roles on surface quality deterioration. A modified roughness evolution mechanism and an improved binary sputtering theory are proposed to describe the polycrystalline sputtering phenomena. The current research can provide a guidance for the application of IBS in aluminum optics manufacture fields.Launching ultrashort femtosecond photoacoustic pulses with multi-terahertz bandwidth will find broad applications from fundamental acoustics in 2D materials and THz-acoustic and phonon spectroscopy to nondestructive detection in opaque materials with a sub-nanometer resolution. Here we report the generation of ultra-short 344 fs photoacoustic pulses with a 2.1 THz bandwidth from interfacial two-dimensional electron gas using optical femtosecond excitation. A comparison with simulation supports the dominant contribution of hot electron pressure and the ultrafast electron relaxation to produce pulsewidth shorter than the acoustic transit time across the electron wavefunction. Our simulation further indicates the possibility to generate less then 200 fs photoacoustic pulse.Mirror-asymmetric split-ring metamaterials with high quality factor in the terahertz (THz) band, consisting of patterned high magnetic permeability and low coercivity FeNHf films deposited on high resistivity silicon substrates, were studied for their magnetic field tunable response in frequency and transmission. Dynamic tuning of terahertz transmission and electromagnetic resonance modes were investigated theoretically and experimentally as a function of magnetization of the FeNHf film. Experimental results indicate that the metamaterial structure provides a giant tunability of resonance frequency (Δfr/fr=3.3%) and transmittivity (21%) at a frequency of 0.665 THz under a low magnetic field of H=100 Oe. Remarkable tuning coefficients of frequency and transmittivity, 0.23 GHz/Oe and 0.21%/Oe, respectively, were measured. Finite difference time domain simulations reveal that the incredible tunability stems predominately from the response of the THz dynamic magnetic field to magnetization. As a result, the metamaterial, consisting of a simple magnetic split-ring microstructure, provides previously unimagined paths to tunable devices for potential use in emerging THz technologies including 6G communication systems and networks.We report the giant enhanced optical harmonic generation in all-dielectric silicon nitride (SiN) based resonant waveguide gratings (RWGs) of quasi-bound states in the continuum (BICs) of ultra-high Q factor and localized field. The BICs are realized by tuning the excitation of the guided modes modulated by geometry parameters of four-part grating layer. At a feasible structure of quasi-BIC for nanofabrication, the SHG and THG are enhanced by 103 and 106, compared with those from the RWGs of traditional two-part grating layer, respectively, and even up to 108 and 1010 compared with those from the planar SiN film, respectively. The resonance wavelength of quasi-BICs can be effectively tuned by the angle of incidence, while almost not affect the enhancement of SHG and THG response. Our results show that the efficiency harmonic generation from all-nonlinear-dielectric RWGs of quasi-BICs has potential applications for the integrated nonlinear photonic devices.The beam splitters are essential optical components that are widely used in various optical instruments. The robustness of beam splitters is very necessary to all-optical networks. Here we report the design of the topologically protected beam splitter, whose splitting ratio can change flexibly to an arbitrary ratio, such as 5050, 3367, 2575, based on the two-dimensional silicon photonic crystal slab. By using the 5050 beam splitter, all major logic gates (OR, AND, NOT, XOR, NAND, XNOR, and NOR) are suitably designed with the linear interference approach. Additionally, these devices exhibit robustness even though some disorders exist. It is expected that these robust and compact devices are potentially applicable in optical computing and signal processing.Laser scanning plays an important role in a broad range of applications. Toward 3D aberration-free scanning, a remote focusing technique has been developed for high-speed imaging applications. However, the implementation of remote focusing often suffers from a limited axial scan range as a result of unknown aberration. Through simple analysis, we show that the sample-to-image path length conservation is crucially important to the remote focusing performance. To enhance the axial scan range, we propose and demonstrate an image-plane aberration correction method. SKF-34288 research buy Using a static correction, we can effectively improve the focus quality over a large defocusing range. Experimentally, we achieved ∼three times greater defocusing range than that of conventional methods. This technique can broadly benefit the implementations of high-speed large-volume 3D imaging.