High-speed mid-wave infrared (MWIR) photodetectors have important applications in the emerging areas such high-precision frequency comb spectroscopy and light detection and ranging (LIDAR). In this work, we report a high-speed room-temperature mid-wave infrared interband cascade photodetector based on a type-II InAs/GaSb superlattice. The devices show an optical cut-off wavelength around 5 µm and a 3-dB bandwidth up to 7.04 GHz. The relatively low dark current density around 9.39 × 10-2 A/cm2 under -0.1 V is also demonstrated at 300 K. These results validate the advantages of ICIPs to achieve both high-frequency operation and low noise at room temperature. Limitations on the high-speed performance of the detector are also discussed based on the S-parameter analysis and other RF performance measurement.In this paper, we quantify the benefits of compensated-beacon adaptive optics (CBAO) relative to uncompensated-beacon adaptive optics (UBAO) using wave-optics simulations. Throughout, we present results for both the Shack-Hartmann wavefront sensor (SH-WFS) and the digital-holographic wavefront sensor (DH-WFS). Given weak to moderately strong scintillation conditions, the results show that the two noiseless sensors offer similar performance in terms of the peak Strehl ratio when using similar subaperture sampling and least-squares phase reconstruction. Specifically, CBAO leads to an average performance boost of 17% for the SH-WFS and 26% for the DH-WFS relative to UBAO for the turbulence scenarios studied here.We proposed an alternative method to design a magnifying lens by optical conformal mapping.  https://www.selleckchem.com/products/cc-930.html  Different from previous hyperlens or superlens, the proposed lens needs no materials with negative or anisotropic refractive index. The lens has better photonic transporting efficiency than conventional a solid immersion lens due to impedance matching. The proposed lenses have many other advantages, such as broadband, low loss, and no need to redesign the sizes and material parameters when another magnifying ratio is required. Both numerical simulations and experimental demonstrations are implemented to verify the performance of the lens.Superconducting nanowire single-photon detector (SNSPD) with near-unity system efficiency is a key enabling, but still elusive, technology for numerous quantum fundamental theory verifications and quantum information applications. The key challenge is to have both a near-unity photon-response probability and absorption efficiency simultaneously for the meandered nanowire with a finite filling ratio, which is more crucial for NbN than other superconducting materials (e.g., WSi) with lower transition temperatures. Here, we overcome the above challenge and produce NbN SNSPDs with a record system efficiency by replacing a single-layer nanowire with twin-layer nanowires on a dielectric mirror. The detector at 0.8 K shows a maximal system detection efficiency (SDE) of 98% at 1590 nm and a system efficiency of over 95% in the wavelength range of 1530-1630 nm. Moreover, the detector at 2.1 K demonstrates a maximal SDE of 95% at 1550 nm using a compacted two-stage cryocooler. This type of detector also shows the robustness against various parameters, such as the geometrical size of the nanowire and the spectral bandwidth, enabling a high yield of 73% (36%) with an SDE of >80% (90%) at 2.1 K for 45 detectors fabricated in the same run. These SNSPDs made of twin-layer nanowires are of important practical significance for batch production.An effective approach is proposed for obtaining a long-distance THz diffraction-free beam with meter-scale length. Multiple 3D-printed lens-axicon doublets are cascaded to form the generation system. In order to manifest the physical mechanism behind the generation process of this long-distance diffraction-free beam, we make a detailed comparative analysis of three beams the ideal Bessel beam, the quasi-Bessel beam generated by single axicon, and the diffraction-free beam generated by the lens-axicon doublets. Theoretical results show that the zero-radial-spatial-frequency component plays a key role during the generation process of the third beam. Moreover, the intensities of this component are enhanced with the increase in the number of lens-axicon doublets, making the diffraction-free length longer. An experiment containing three lens-axicon doublets is performed to demonstrate the feasibility of our design. A 0.1-THz beam with one-meter diffraction-free length was successfully generated. Further experiments indicate that this THz diffraction-free beam also has a self-healing property. We believe that such long-distance diffraction-free beams can be used in practical THz remote sensing or imaging.Dynamic coherent diffractive imaging (CDI) reveals the fine details of structural, chemical, and biological processes occurring at the nanoscale but imposes strict constraints on the object distribution and illumination. Ptychographic CDI relaxes these constraints by exploiting redundant information in data obtained from overlapping regions of an object, but its time resolution is inherently limited. We have extended ptychographic redundancy into the spatiotemporal domain in dynamic CDI, automatically identifying redundant information in time-series coherent diffraction data obtained from dynamic systems. Simulated synchrotron experiments show that high spatiotemporal resolution is achieved without a priori knowledge of the object or its dynamics.We present a novel phase generated carrier (PGC) demodulation technique for homodyne interferometers which is robust to modulation depth variations and source intensity fluctuations. By digitally mixing the waveform with a multitone synthetic function (a linear combination of harmonics of the modulating signal), distortion can become negligible even in presence of large variations of the modulation depth. The technique only requires two mixers and can also provide the DC component of the phase in real time, without needing any previously recorded data or ellipse-fitting algorithms. We validate the technique with simulated waveforms and with experimental data from a wavelength metering experiment using an integrated unbalanced interferometer on-chip, showing that the technique corrects distortion without increasing the noise with respect to the standard PGC technique.