光学干涉仪是现代精密测量技术的核心支撑，但其分辨率受到光源波长的限制，无法通过无限减小波长提高分辨率，而“相位超分辨”即是指设法解决光源波长限制的技术手段。目前“相位超分辨”研究主要通过调控 $ N $光子纠缠态的途径实现，但是由于 $ N $光子纠缠态制备与调控的极高难度和符合计数的极低效率使得该途径无法用于实际测量。针对这一瓶颈，笔者联合团队利用轨道角动量（OAM）相干态在光学超晶格中的级**量上转换过程高效构造、提取多光子复振幅信号。实现了 $ N=12 $倍的相位超分辨干涉信号的实时测量，为发展可实际应用的高倍率相位超分辨干涉测量技术提供了一条全新的物理途径。

Laguerre-Gaussian (LG) modes, carrying the orbital angular momentum of light, are critical for important applications, such as high-capacity optical communications, superresolution imaging, and multidimensional quantum entanglement. Advanced developments in these applications demand reliable and tunable LG mode laser sources, which, however, do not yet exist. Here, we experimentally demonstrate highly efficient, highly pure, broadly tunable, and topological-charge-controllable LG modes from a Janus optical parametric oscillator (OPO). The Janus OPO featuring a two-faced cavity mode is designed to guarantee an efficient evolution from a Gaussian-shaped fundamental pump mode to a desired LG parametric mode. The output LG mode has a tunable wavelength between 1.5 and 1.6 μm with a conversion efficiency >15 % , a controllable topological charge up to 4, and a mode purity as high as 97%, which provides a high-performance solid-state light source for high-end demands in multidimensional multiplexing/demultiplexing, control of spin-orbital coupling between light and atoms, and so on.

涡旋光激光器能够输出具有特定空间结构的高能量、高质量的涡旋光束。涡旋光束在光通讯、光操控、超分辨成像等领域都有潜在的应用前景。本文介绍了涡旋光束的产生原理及其应用，综述了近期涡旋光激光器的发展历程，同时也对涡旋光激光器的发展趋势进行了展望。

We study the effect of dimension variation for second-harmonic generation (SHG) in lithium niobate on insulator (LNOI) waveguides. Non-trivial SHG profiles in both type-0 and type-I quasi-phase matching are observed during the wavelength tuning of the fundamental light. Theoretical modeling shows that the SHG profile and efficiency can be greatly affected by the waveguide cross-section dimension variations, especially the thickness variations. In particular, our analysis shows that a thickness variation of tens of nanometers is in good agreement with the experimental results. Such investigations could be used to evaluate fabrication performance of LNOI-based nonlinear optical devices.

Periodically poled lithium niobate on insulator (LNOI) ridge waveguides are desirable for high-efficiency nonlinear frequency conversions, and the fabrication process of such waveguides is crucial for device performance. In this work, we report fabrication and characterization of locally periodically poled ridge waveguides. Ridge waveguides were fabricated by dry etching, and then the high-voltage pulses were applied to locally poled ridge waveguides. Second harmonic generation with normalized conversion efficiency of 435.5% W^-1·cm^-2 was obtained in the periodically poled LNOI ridge waveguide, which was consistent with the triangular domain structure revealed by confocal microscopy.

We report efficient generation of 671 nm red light based on quasi-phase-matched second harmonic generation of 1342 nm in LiNbO₃ waveguides. The design method and fabrication process of the high-quality annealed proton-exchanged periodically poled channel waveguides were presented. A continuous-wave 1.71 mW red light was obtained with a single-pass conversion efficiency of 47%·W^-1·cm^-2, which is 88% that of the theoretical value. While for 1 mW quasi-continuous-laser input, the corresponding peak power being 2 W, the conversion efficiency reached up to 60%. Our results indicate that the annealed proton-exchanged periodically poled LiNbO₃ waveguide is promising for high-efficiency and low power consumption nonlinear generation of visible light.

In this work, we propose a new scheme to generate frequency-doubled vortex beams from a radially poled LiNbO₃ micro-ring resonator based on nonlinear Cherenkov radiation. The near-infrared fundamental wave is resonant in the micro-ring, while the second harmonic is emitted from the resonator along the Cherenkov phase-matching direction. The topological charge of the emitted second-harmonic vortex beam is determined by both the azimuthal order of the whispering galley modes and the number of nonlinear grating elements. The field distribution and the conversion efficiency of the emitted vortex beam are investigated.

We report the fabrication of an MoS2 black phosphorus (BP) composite saturable absorber by liquid phase exfoliation and the spin-coating method and further exploitation to build a 2 μm passively Q-switched Tm:YAP laser. Such a composite based Q-switched laser with a duration of 488 ns and corresponding peak power of 85.9 W is obtained, which shows an improved saturable absorption effect than that of single MoS2 (616 ns, 68.7 W) and BP (932 ns, 22.4 W). The results indicate that simple and reasonable fabrication of the vertical composite from two-dimensional atomic layer materials opens up the possibility to create an unprecedented saturable absorber with exciting properties.