An on-chip optical phased array (OPA) is considered as a promising solution for next generation solid-state beam steering. However, most of the reported OPAs suffer from low operating bandwidths, making them limited in many applications. We propose and demonstrate a high-speed 2D scanning OPA based on thin-film lithium niobate phase modulators with traveling-wave electrodes. The measured modulation bandwidth is up to 2.5 GHz. Moreover, an aperiodic array combined with a slab grating antenna is also used to suppress the grating lobes of far-field beams, which enables a large field of view (FOV) as well as small beam width. A 16-channel OPA demonstrates an FOV of 50°×8.6° and a beam width of 0.73°×2.8° in the phase tuning direction and the wavelength scanning direction, respectively.

载波调制水下探测激光雷达利用散射光和信号光在频域特性上的差异来抑制杂散光，而不同水质中的散射光的截止频率是载波调制水下探测激光雷达设计中的重要参数。测量散射杂波的频率响应需要将目标回波与散射杂波分开，尤其是前向散射，与目标回波空间上重合，不容易被分开。文中提出了一种在载波强度调制激光雷达中分别测量水下目标和散射杂波的频率响应方法，利用散射光和目标反射的信号光在空间相干性上的差异，在回波光路上使用螺旋相位板将其分开并分别采集，再通过傅里叶变换得到它们的频谱。实验结果表明，前向散射杂波具有低通特性，而目标回波的响应是平坦的。将信号与散射在频谱中调制频率处的幅度之比定义为“信杂比”，并且用其来表示探测的有效性：当信杂比大于1时，认为探测到了目标。在较浑浊的水中，为了获得大于1的信杂比，载波的调制频率需要更高，基于蒙特卡洛方法对光子在海水中的传播进行了仿真模拟，结果与实验相符。测距实验也证明了，提高调制频率可以减小浑浊水中的测距误差。当信杂比小于1时，提高调制频率，测距误差降低明显。

Chip-scale programmable optical signal processors are often used to flexibly manipulate the optical signals for satisfying the demands in various applications, such as lidar, radar, and artificial intelligence. Silicon photonics has unique advantages of ultra-high integration density as well as CMOS compatibility, and thus makes it possible to develop large-scale programmable optical signal processors. The challenge is the high silicon waveguides propagation losses and the high calibration complexity for all tuning elements due to the random phase errors. In this paper, we propose and demonstrate a programmable silicon photonic processor for the first time by introducing low-loss multimode photonic waveguide spirals and low-random-phase-error Mach-Zehnder switches. The present chip-scale programmable silicon photonic processor comprises a 1×4 variable power splitter based on cascaded Mach-Zehnder couplers (MZCs), four Ge/Si photodetectors, four channels of thermally-tunable optical delaylines. Each channel consists of a continuously-tuning phase shifter based on a waveguide spiral with a micro-heater and a digitally-tuning delayline realized with cascaded waveguide-spiral delaylines and MZSs for 5.68 ps time-delay step. Particularly, these waveguide spirals used here are designed to be as wide as 2 μm, enabling an ultralow propagation loss of 0.28 dB/cm. Meanwhile, these MZCs and MZSs are designed with 2-μm-wide arm waveguides, and thus the random phase errors in the MZC/MZS arms are negligible, in which case the calibration for these MZSs/MZCs becomes easy and furthermore the power consumption for compensating the phase errors can be reduced greatly. Finally, this programmable silicon photonic processor is demonstrated successfully to verify a number of distinctively different functionalities, including tunable time-delay, microwave photonic beamforming, arbitrary optical signal filtering, and arbitrary waveform generation.

A compact on-chip reconfigurable multichannel amplitude equalizer based on cascaded elliptical microrings is proposed and demonstrated experimentally. With the optimized structure of the elliptical microring with adiabatically varied radii/widths, the average excess loss for each channel in the initialized state is measured to be less than 0.5 dB, while the attenuation dynamic range can be over 20 dB. Flexible tunability through the overlapping of the resonance peaks of adjacent wavelength-channels enables even higher attenuation dynamic ranges up to 50 dB. Leveraging the thermo-optic effect and fine wavelength-tuning linearity, precise tuning of the resonance peak can be implemented, enabling dynamic power equalization of each wavelength-channel in wavelength-division-multiplexing (WDM) systems and optical frequency combs. The proposed architecture exhibits excellent scalability, which can facilitate the development of long-haul optical transport networks and high-capacity neuromorphic computing systems, while improving the overall performance of optical signals in WDM-related systems.

石墨烯和其他二维材料凭借其自身独特的物理和化学性能，引起了科学和工程领域的广泛关注。探索新型二维材料体系并扩展其应用范围是研究人员的热点研究内容。其中，第五主族单元素二维烯（二维磷烯、二维砷烯、二维锑烯、二维铋烯）具有较窄的且可调节的能带宽度、高的载流子迁移率、良好的透光性和优异的光电子学性能，成为二维材料及其在光电子应用领域的新的研究对象。鉴于此方面，从基本物理结构、材料的制备方法和在光电子方面的应用深入分析二维铋烯的相关理论以及实验研究的工作进展。在材料的可控制备方面，重点围绕二维铋烯的电化学剥离法展开相应论述。最后讨论了二维铋烯在光电子学应用领域的现状，包括在超快光电子学器件的应用，并且对二维铋烯未来的发展进行了展望。