A power balanced dual-wavelength laser (DWL) based on the Nd:GdVO ₄ crystal is presented. The orthogonally polarized gain spectral evolution of the Nd:GdVO ₄ crystal versus the temperature is studied, and the power balancing conditions of the DWLs are theoretically analyzed firstly. In the experiments, by using two output couplers and a temperature controller, the power balanced Nd:GdVO ₄ DWL signals at 1063 nm (π) and 1065 nm (σ) are obtained with the crystal heat sink temperature ( T _c ) from 20 °C to 40 °C. The experimental results show, with the pump power at 9.3 W and T _c at 25 °C, the DWL signal of the balanced power at 0.78 W for each wavelength and the frequency separation at 0.62 THz is realized. The beam quality M ² of the π- and σ-polarized DWL signals are measured between 2.1 to 2.4.

The dependence of the symmetries of Hermite-Gaussian (HG) mode on system loss is theoretically analyzed through intracavity resonant mode superpositions. In the experiments, asymmetrical HGm,0 modes of m=0-9 are obtained using an off- axis pumped Nd: YVO4 laser with different output mirror reflectivities, and their symmetries are quantitatively analyzed. Experimental results demonstrate that as the output mirror reflectivity decreases from 95% to 81%, 60%, and 50%, the symmetries of the HG mode reach 93%, 70%, 43%, and 14%, respectively, consistent with numerical simulation results. The symmetry of the Laguerre-Gaussian (LG) beam obtained through an astigmatic mode converter (AMC) is almost identical to that of HG. Furthermore, the output powers of asymmetrical LG modes with different transverse orders exceed 1 W with a pump power of 6.36 W. These high-power asymmetrical LG modes are useful in the research of asymmetrical vortex beams.

This study investigates the influence of the thermal lens effect on the characteristics of Laguerre–Gauss (LG) modes in an off-axis pumped solid-state laser. The experiment directly generated LG₀₁−LG₀₇ laser modes through off-axis pumping. The results indicate that the thermal lens effect leads to mode hopping in the LG modes. As the crystal temperature increases, the LG modes transition from a single mode to a mixed mode and then hop to adjacent lower-order LG modes, with the temperature of the crystal heat sink being negatively correlated with the mode order during hopping. This phenomenon is attributed to the off-axis pumping causing a shift in the optical axis of the resonator, which reduces the effective off-axis amount. By adjusting the off-axis amounts of each LG mode, the mode hopping issue was effectively resolved, resulting in a stable output of 1.52 W for the LG₀₇ beam at a pump power of 6.5 W.

Single-photon frequency conversion in the system composed of a Λ-type three-level giant atom chiral couples to a one-dimensional waveguide is investigated. Two configurations, i.e., one of the atomic transitions couples to the waveguide at two separated points while the other one either directly or indirectly couples to the waveguide at a single point, are considered. The scattering amplitudes for representing the frequency conversion in the two kinds of coupling schematics are obtained analytically with the real-space approach. The results show that perfect nonreciprocal transmission with preserving frequency and ideal directional frequency conversion can be realized due to the time-reversal symmetry broken induced by the chiral coupling as well as the self-interference comes from the giant atom. In particular, in the indirect coupling configuration, the scattering spectra exhibit two directional frequency conversion windows due to the atom-cavity coupling, which enables the present system suitable for the simultaneous manipulation of incident photons with different frequencies. These results may have potential applications in various quantum information processing and quantum network engineering.

Frequency-modulated continuous wave (FMCW) LiDAR features high resolution and strong anti-interference ability, yet its performance is limited by the laser frequency sweep nonlinearity. In this paper, a nonlinear correction method based on time–frequency analysis is proposed, which combines the generalized parametric Stockwell transform (GPST) with the synchrosqueezing transform (SST) and applies phase compensation to the beat signal. For 100 repeated ranging experiments on a fixed target at 1 m, the standard deviation of the measurement error is only 0.3 mm. This study provides an effective technical solution for improving the measurement performance of FMCW LiDAR.