全固态单频连续波激光器因其噪声低、线宽窄、光束质量好、功率稳定性高等优点已经被广泛应用于产生非经典光场、冷原子物理研究、引力波探测等诸多领域。随着科学技术的不断发展，传统的全固态激光器的输出功率已经不能满足前沿领域的需求，因此亟需在保持全固态激光器整体性能的同时进一步提升激光器的输出功率。为此首先需要更高的泵浦功率，而这将使激光器内部增益提高，在腔内损耗不变的情况下，原非振荡模式也将满足起振条件，从而使激光器在跳模或多模状态下运转。此外，激光晶体的热效应和损伤阈值也限制了输出功率的提高。本文介绍了一种利用非线性损耗大幅度提升全固态单频连续波激光器的输出功率的技术和方法。通过在谐振腔中引入非线性损耗，使主模经受的非线性损耗是次模的一半。在模式竞争的作用下，谐振腔内的模式被更进一步的选择，从而允许全固态单频激光器在更高的增益下保持单纵模运转。通过在谐振腔内插入多块增益晶体可以有效缓解由于激光增益晶体热效应的限制，从而实现更高功率的单频激光输出。目前高功率全固态连续波激光器的输出功率已经达到了一百瓦的量级，且还在进一步提高。通过在谐振腔内引入非线性损耗，全固态单频连续波激光器的整体性能在得以保障和提高的同时，其应用范围也得到了进一步的推广。

We present a continuously tunable high-power continuous wave (CW) single-frequency (SF) Nd:YAlO3/lithium triborate (Nd:YAP/LBO) laser with dual-wavelength output, which is implemented by combining an optimized and locked etalon with an intracavity nonlinear loss. The obtained output powers of the stable SF 1080 and 540 nm lasers are 2.39 and 4.18 W, respectively. After the etalon is locked to an oscilating mode of the laser, the wideband continuous frequency tuning and long-term stable single-longitudinal-mode operation of the laser are successfully realized, which can be well used for the applications of quantum information and quantum computation. To the best of our knowledge, this is the first realization of the continuously tunable high-power CW SF 1080/540 nm dual-wavelength laser.

Multi-beam laser processing is a very popular method to improve processing efficiency. For this purpose, a compact and stable multi-beam pulsed 355 nm ultraviolet (UV) laser based on a micro-lens array (MLA) is presented in this Letter. It is worth noting that the MLA is employed to act as the spatial splitter as well as the coupling lens. With assistance of the MLA, the 1064 nm laser and 532 nm laser are divided into four sub-beams and focused at different areas of the third-harmonic generation (THG) crystal. As a result, the multi-beam pulsed 355 nm UV laser is successfully generated inside the THG crystal. The measured pulse widths of four sub-beams are shorter than 9 ns. Especially, the generated four sub-beams have good long-term power stability benefitting from the employed MLA. We believe that the generated stable multi-beam 355 nm UV laser can meet the requirement of high-efficiency laser processing, and the presented method can also pave the way to generate stable and long-lived multi-beam UV lasers.

We demonstrate an all-solid-state continuous-wave (CW) single-frequency tunable 1.08 µm laser, which is realized by employing a disordered laser medium Nd:CaYAlO₄ (Nd:CYA) crystal. The maximal output power of single-frequency 1.08 µm laser is 1 W. By rotating the incident angle of the intracavity etalon (IE), the maximal tuning range of 183.71 GHz is achieved. After the IE is locked to the oscillating longitudinal mode of the laser, the continuous tuning range of 60.72 GHz for 1.08 µm laser is achieved by scanning the cavity length. To the best of our knowledge, this is the first demonstration of a CW single-frequency widely tunable 1.08 µm laser based on Nd:CYA crystal.

A scheme for measuring the intra-cavity round-trip loss of an all-solid-state single-frequency laser by inserting a type-I noncritical phase-matching nonlinear crystal introducing nonlinear loss into the resonator is presented. The intra-cavity round-trip loss is theoretically deduced by analyzing the dependence of the fundamental-wave (FW) and second-harmonic-wave (SHW) powers on the pump factor and the nonlinear conversion factor of the single-frequency laser and experimentally measuring them by recording different FW and SHW powers, which are decided by the temperature of the nonlinear crystal. The measured intra-cavity round-trip loss and pump factor are 4.84% and 6.91% W 1, respectively. The standard deviations of the measured intra-cavity round-trip loss and the pump factor are 0.26% and 0.07%, respectively. This scheme is very suitable for measuring the intra-cavity round-trip loss of a high-gain solid-state single-frequency laser.