We present the frequency control of a 759 nm laser as a lattice laser for an ytterbium (Yb) optical clock. The frequency stability and accuracy are transferred from the Yb optical clock via an optical frequency comb. Although the comb is frequency-stabilized on a rubidium microwave clock, the frequency instability of the 759 nm laser is evaluated at the 10-15 level at 1 s averaging time. The frequency of the 759 nm laser is controlled with an uncertainty within 1 Hz by referencing to the Yb clock transition. Such a frequency-controlled 759 nm laser is suitable for Yb optical clocks as the lattice laser. The technique of laser frequency control can be applied to other lasers in optical clocks.

The resolution of the spatial light modulator (SLM) screen and the encoding algorithm of the computer-generated hologram are the primary limiting factors in the generation of large topological charge vortex beams. This paper attempts to solve these problems by improving both the hardware and the algorithm. Theoretically, to overcome the limitations of beam waist radius, the amplitude profile function of large topological charge Laguerre–Gaussian (LG) beam is properly improved. Then, an experimental system employing a 4K phase-only SLM is set up, and the LG beams with topological charge up to 1200 are successfully generated. Furthermore, we discuss the effect of different beam waist radii on the generation of LG beams. Additionally, the function of the LG beam is further improved to generate an LG beam with a topological charge as high as 1400. Our results set a new benchmark for generating large topological charge vortex beams, which can be widely used in precise measurement, sensing, and communication.

In the integral imaging light field display, the introduction of a diffractive optical element (DOE) can solve the problem of limited depth of field of the traditional lens. However, the strong aberration of the DOE significantly reduces the final display quality. Thus, herein, an end-to-end joint optimization method for optimizing DOE and aberration correction is proposed. The DOE model is established using thickness as the variable, and a deep learning network is built to preprocess the composite image loaded on the display panel. The simulation results show that the peak signal to noise ratio value of the optimized image increases by 8 dB, which confirms that the end-to-end joint optimization method can effectively reduce the aberration problem.

We present and demonstrate a multifunctional single-fiber optical tweezer for particle trapping and transport. The fiber probe of fiber optical tweezers is constructed as a planar structure. Laser sources with wavelengths of 650 nm and 980 nm in a single-mode fiber excite the linearly polarized LP11 mode and LP01 mode beams, respectively. These two laser beams can achieve non-contact trapping and long-distance transport of particles after passing through a flat-facet fiber probe, respectively. This structure makes it possible to perform non-contact trapping and transport of particles by combining multiple wavelengths and multiple modes.

A 2-mm-long silicon-on-insulator grating emitter with a narrow angular full width at half-maximum (FWHM) and a high sideband suppression ratio (SSR) is proposed and designed. It consists of a Si3N4/Si grating with an approximate Gaussian emission profile along the grating length, which aims to reduce the sidelobe intensity of the scanning light in the far-field, thereby improving the resolution of the longitudinal steering resolution of the light detection and ranging (lidar). Numerical analysis shows that the angular FWHM of the emitted beam could be as low as 0.026° for a grating length of 2.247 mm and the input TE-like waveguide mode at 1550 nm, and the SSR could be more than 32.622 dB. Moreover, this Si3N4/Si grating exhibits a favorable fabrication error tolerance when considering the width and length variation of the Si3N4 overlayer in practice. Our design offers a promising platform for realizing integrated optical phased arrays for the long-distance solid-state lidar.

A continuous-wave (CW) π-polarized 1084 nm laser based on Nd:MgO:LiNbO3 under 888 nm thermally boosted pumping is reported. According to the absorption spectrum and energy level structure of Nd:MgO:LiNbO3, the 888 nm laser diode (LD) is used for thermally boosted pumping. This pumping method eliminates the quantum defect caused by the nonradiative transition in Nd:MgO:LiNbO3 under the traditional 813 nm pumping and effectively improves the serious thermal effect of the crystal. The unmatched polarized 1093 nm laser is completely suppressed, and the π-polarized laser output of 1084 nm in the whole pump range is realized by the 888 nm thermally boosted pumping. In the present work, we achieved the CW π-polarized 1084 nm laser with a maximum output power of 7.53 W and a slope efficiency of about 46.1%.

Four single crystals (Yb_0.15Lu_0.85xY_0.85-0.85x)₃Al₅O₁₂ (x = 0, 0.25, 0.5, 1) were grown by the Czochralski method. The correlation of the host atom Lu:Y ratios with the density and the luminescence properties were revealed. The density increases linearly with increasing of Lu3+ content, which will improve the gamma ray cut-off ability. The integrated intensity of the X-ray excited luminescence spectrum increases exponentially with the increasing Y:Lu ratio, while the decay time becomes even shorter with the increasing Lu3+ content. These results will provide a basis to balance the comprehensive properties to match different application requirements.

Depressed cladding waveguides are fabricated in Pr:LiYF₄ (YLF) crystal by femtosecond laser inscription following a helical scheme. With the optimized parameters, the propagation loss of the waveguide is around 0.12 dB/cm for multimode guiding. Under optical pumping with InGaN laser diodes at 444 nm, efficient waveguide lasers in the orange around 604 nm (π-polarized) are achieved with minimum lasing threshold of 119.8 mW, maximum slope efficiency of 16.6%, and maximum output power of 120.6 mW. Benefiting from their optimized performances, the waveguides produced in this work are promising for applications as compact orange laser sources.

We propose a method for detecting the symmetry of rotating patterns based on the rotational Doppler effect (RDE) of light. The basic mechanisms of the RDE are introduced, and the spiral harmonic distribution of rotating patterns is analyzed. By irradiating the rotating pattern using a superimposed optical vortex and analyzing the amplitude of the RDE signal, the spiral harmonic distribution of the pattern can be measured, and then its symmetry can be detected. We demonstrate this method experimentally by using patterns with different symmetries and shapes. As the method does not need to receive the scattered light completely and accurately, it promises potential application in detecting symmetrical rotating objects at a long distance.

The quantum key distribution (QKD) network is a promising solution for secure communications. In this paper, we proposed a polarization-independent phase-modulated polarization encoding module, and it can be combined with a dense wavelength division multiplexer (DWDM) to achieve multi-user QKD. We experimentally test the encoding module with a repetition rate of 62.5 MHz, and its average quantum bit error rate (QBER) is as low as 0.4%. Finally, we implement a principle verification test for simultaneous QKD for 1 to 2 users in 100 min, and the average QBER of two users under the transmission distance of 1 km and 5 km is kept below 0.8%. Due to the use of polarization encoding, the module can also realize scalable network architecture in free-space QKD systems in the future.

The ultracold molecule is a promising candidate for versatile quantum tasks due to its long-range interaction and rich internal rovibrational states. With the help of the cavity quantum electrodynamics (QED) effects, an optical cavity can be employed to increase the efficiency of the formation of the photoassociated molecules and offers a non-demolition detection of the internal states of molecules. Here, we demonstrate the production of the high-finesse optical fiber microcavity for the Rb2 molecule cavity QED experiment, which includes the fabrication of fiber-based cavity mirrors, testing, and the assembly of ultra-high vacuum-compatible optical fiber microcavity. The optical fiber microcavity offers high cooperativity between cavity mode and ultracold molecule and paves the way for the study of molecule cavity QED experimental research.

The optical vortex beam has widely been studied and used because of its unique orbital angular momentum (OAM). To generate and control OAM in compact and integrated systems, many metallic metasurface devices have been proposed, however, most of them suffer from the low efficiency. Here, we propose and experimentally verify a high-efficiency monolayer metallic metasurface composed of semicircular nano-grooves distributed with detour phase. The metasurface can generate single or an array of OAM with spin-sensitive modulation and achieve the maximum efficiency of 60.2% in theory and 30.44% in experiment. This work has great potential in compact OAM detection and communication systems.