一、本期重点：
1.基于波前整型的光学模拟白内障校正（Wavefront-shaping-based correction of optically simulated cataracts）【optica】
Doi: 10.1364/OPTICA.7.000022
Published: January 3, 2020
内容介绍：
白内障是一种常见的眼部病理，其中晶状体趋于变得不透明，由于像差和散射的增加而降低了视网膜图像的质量。
在这项工作中，研究人员使用液晶装置空间光调制器同时生成并光学校正了光具座中的白内障的影响。通过实施基于反馈的波前整形技术进行校正，校正器相位图的空间分辨率不同。通过视觉质量的主观和客观描述来评估其益处。除了对未校正和校正后的眼点扩散函数进行数值计算外，还对实验结果进行了分析和体内应用。
图一：基于以下几种情况的视野模拟：（a）清晰的光学成像，（b）晚期的白内障影响，（c）通过WS算法的初步校正，（d）所提出的简化方式，（e）增强对比度后的图像。
2. 无需线性校准即可进行一般线性成像偏振法的迭代重建（Iterative reconstruction for general linear imaging polarimetry without polarimetric calibration）【Optics Letters】
Doi: 10.1364/OL.45.000057
Published: December 16, 2019
内容介绍：
通常，为了精确重建斯托克斯参数，需要使用一组标准偏振态对成像偏振计的实际分析状态进行校准。然而，获得用于偏振校准的标准元件是具有挑战性的。
这篇文章首次提出一种迭代重建方法，以从线性斯托克斯旋光仪获得的数据中恢复偏振参数，而无需进行偏振校准。受相移干涉法的启发，该方法采用了两个最小二乘迭代程序，不需要额外的辅助元素。实验结果表明，与参考偏振态下的标定方法相比，该迭代方法对噪声扰动具有更强的鲁棒性，并且具有较高的精度。
图一：实验装置。P1、P2：可旋转的线性偏振器；BF：带通滤波器。使用卤素灯产生均匀扩展的非偏振光源，如积分球所示。
二、简讯：
1.基于通过稀疏约束的鬼成像的单幅大视场纳米显微技术（Single-frame wide-field nanoscopy based on ghost imaging via sparsity constraints）【optica】
Doi: 10.1364/OPTICA.6.001515
Published: December 12, 2019
Abstract::
Single-molecule, localization-based, wide-field nanoscopy often suffers from low time resolution because the localization of a single molecule with high precision requires a low emitter density of fluorophores. In addition, to reconstruct a super-resolution image, hundreds or thousands of image frames are required, even when advanced algorithms, such as compressive sensing and deep learning, are applied. These factors limit the application of these nanoscopy techniques for living cell imaging. In this study, we developed a single-frame, wide-field nanoscopy system based on ghost imaging via sparsity constraints (GISC), in which a spatial random phase modulator is applied in a wide-field microscope to achieve random measurement of fluorescence signals. This method can effectively use the sparsity of fluorescence emitters to enhance the imaging resolution to 80 nm by reconstructing one raw image using compressive sensing. We achieved an ultrahigh emitter density of 143 μm-2.
2. 直接在硅上生长的可调谐量子点激光器（Tunable quantum dot lasers grown directly on silicon）【optica】
Doi: 10.1364/OPTICA.6.001394
Published: October 25, 2019
Abstract:
Tunable semiconductor lasers are often listed in critical technology road maps for future dense-wavelength-division-multiplexing (DWDM) systems and high-performance computing systems, and they are increasingly demanded in long-haul, metropolitan, and access networks. The capability to produce such lasers directly on silicon (Si) could boost the use of Si photonics and facilitate the adoption of optical data transmission even at the chip scale. Moreover, just the use of Si as a cheap and large-diameter substrate for device production is very advantageous, as the fabrication can take advantage of the highly optimized processing techniques and economy of scale enabled by decades of development in Si microelectronics. Here, we report a tunable single-wavelength quantum dot (QD) laser directly grown on Si. The high carrier confinement and a real dot density of QDs provide reduced sensitivity to crystalline defects, which allows for exceptional lasing performance even in lattice-mismatched material systems. The discrete density of states of dots yields unique gain properties that show promise for improved device performance and new functionalities relative to the quantum well counterparts, including high temperature stability, low threshold operation, reduced sidewall recombination, and isolator-free stability. We implement a simple, integrable architecture to achieve over 45 dB side-mode-suppression-ratio without involving regrowth steps or subwavelength grating lithography. Under continuous-wave electrical injection at room temperature, we achieved a 16 nm tuning range with output powers of over 2.7 mW per tuning wavelength. This work represents a step towards using III–V/Si epitaxy to form efficient, easily manufacturable on-chip Si light sources for not only DWDM networks, but also spectroscopy, biosensors, and many other emerging applications.
3. 由超短中红外激光脉冲驱动的紫外到毫米带超连续谱（Ultraviolet-to-millimeter-band supercontinua driven by ultrashort mid-infrared laser pulses）【optica】
Doi: 10.1364/OPTICA.7.000015
Published: January 3, 2020
Abstract:
Combined optical nonlinearity of bound and free electrons in a fast-ionizing medium driven by ultrashort, mid-infrared (mid-IR) pulses gives rise to a vast variety of ultrafast nonlinear-optical scenarios, producing bright, broadband radiation in spectral ranges as different as ultraviolet (UV) and terahertz (THz). Given its enormous bandwidth, a quantitative experimental analysis of this type of nonlinear response is anything but simple. Here, we confront this challenge by ultrabroadband spectral measurements performed across the spectral range from the UV to the millimeter-wave (MMW) band jointly with beam profile analysis in the THz-to-MMW band and direct time-domain field waveform characterization. As one of the most striking results, the nonlinear response of a fast-ionizing gas driven by a two-color field, consisting of a high-peak-power sub-100-fs mid-IR pulse and its second harmonic, is shown to provide a source of a bright multiband supercontinuum (SC) radiation, whose spectrum spans over about 14 octaves, stretching from below 300 nm all the way beyond 4.3 mm. The MMW-to-THz part of this SC is emitted, as direct measurements show, in the form of half-cycle field waveforms that can be focused to yield a field strength of ≈5MV/cm. At least 1.5% of the MMW–THz supercontinuum energy is emitted in the MMW range, giving rise to MMW field strengths up to 100 kV/cm in the beam waist region.
4.龙卷风波（Tornado waves）【Optics Letters】
Doi: 10.1364/OL.45.000280
Published: January 6, 2020
Abstract:
We show that light spiraling like a tornado can be generated by superimposing abruptly auto-focusing ring-Airy beams that carry orbital angular momentum of opposite handedness. With different parabolic propagation trajectories, the superimposing ring-Airy beams are tailored to abruptly auto-focus at overlapping focal regions. This results in a complex wave with intense lobes that twist and shrink in an accelerating fashion along propagation. By achieving angular acceleration values that exceed 295 rad/mm2, these tornado waves can find numerous applications in laser trapping, direct laser writing, and high-harmonic generation.
