高功率、高光束质量的全固态 355 nm 紫外（UV）激光器因其具有短波长、易聚焦、高能量等特点，已经广泛应用于精细加工、生物医学、光学制造、光学传感等领域。最常用的实现 355 nm 紫外光输出的技术手段是使用主振荡功率放大器（MOPA）系统，该系统首先对 1064 nm 的种子光进行单级或多级放大，然后在腔外通过三倍频频率变换来获得所需的紫外光。2010 年，Yan 等采用由 Nd∶YVO4 组成的 MOPA 对种子源进行功率放大，然后通过级联二倍频和三倍频过程，获得了 35.1 W 的 355 nm 紫外激光输出，泵浦光到紫外光的光-光转换效率为 13%。为了提高三倍频过 程 中 的 转 换 效 率 ，2013 年 ，Chen 等利 用 单 频1064 nm 激光器作为种子光源，通过光纤 MOPA 和固体 MOPA，实现了 43.7 W 的 355 nm 紫外激光输出，泵浦光到紫外光的光-光转换效率提高到 18.2%。尽管采用 MOPA 对基频光进行单级或多级放大，再通过腔外三倍频技术可以保证 355 nm 紫外激光的高功率输出，但是系统整体相对复杂，不利于获得高稳定的紫外激光。另外，为了提高三倍频过程中的转换效率，通常会缩小基频光和倍频光在三倍频晶体处的腰斑尺寸以提高二者的功率密度，由此导致三倍频晶体端面的镀膜涂层在高功率密度激光长时间照射下极易损伤。与腔外三倍频技术相比，腔内三倍频技术不仅可以充分利用腔内基频光功率密度高的优点，而且激光器整体结构紧凑、稳定性高，是实现高功率高稳定性全固态 355 nm 紫外激光器的有效手段之一。同时，为了延长三倍频晶体的使用寿命，研究者采用布儒斯特角切割的三硼酸锂（LBO）晶体作为腔内三倍频频率变换的非线性介质。但是布儒斯特角的引入会导致基频光产生像散，进而影响 355 nm 输出光束质量和转换效率。因此，2019 年，Yang 等设计了凸凹镜相结合的谐振腔结构，有效补偿了布儒斯特角切割的 LBO 晶体引入的像散，获得了 3.65 W 的 355 nm 紫外激光输出 ，横 向 光 束 质 量 因 子（Mx2）和 纵 向 光 束 质 量 因 子（My2）分别为 1.32 和 1.14。2023 年，Xu 等利用一种由平凸镜构成的折叠谐振腔结构，通过采用级联 LBO晶体实现了频率变换，获得了 12.2 W 的 355 nm 紫外激光输出。尽管该工作通过使用凸面入射镜优化了谐振腔的工作稳区，但是由于三倍频晶体采用端面为布儒斯特角切割的 LBO 晶体，其输出的 355 nm 紫外激光的 Mx2 和 My2 分别为 1.18 和 1.24。为了获得高功率高光束质量的 355 nm 紫外激光输出，我们设计了四镜折叠腔结构，通过使用可实现走离补偿的腔内级联非线性 LBO 晶体，提高了 355 nm 紫外激光的输出功率和转换效率，获得的 355 nm 紫外激光的光束质量因子优于 1.18。

An all-solid-state single-frequency continuous-wave (CW) 355 nm ultraviolet (UV) laser based on a dispersion compensated doubly resonant resonator is presented in this Letter that is achieved by employing homemade high-stability all-solid-state frequency-correlated dual wavelength lasers at 1064 and 532 nm and a temperature controlled type-I critical-phase-matching LiB3O5 (LBO) to act as the fundamental laser source and the nonlin ear medium, respectively. The frequency-correlated dual wavelength single-frequency CW laser supplies the fun damental frequency 1064 and 532 nm lasers with good frequency synchronization. And the temperature-controlled LBO acts as the dispersion-compensation element to real ize double resonance of the 1064 and 532 nm laser. Finally, a 4.2 W high-stability 355 nm UV laser is experimentally obtained, and the corresponding total conversion efficiency is up to 20.5%. To the best of our knowledge, this is the highest power reported about single-frequency CW 355 nm UVlaser. The presented method can pave a way to develop a compactsingle-frequency 355 nm UVlaserwithhighoutput power.

Quantum state transmission and quantum information transmission (QIT) through fiber channels hold immense promise for advancing the scope of quantum information applications. However, besides unavoidable transmission loss, channel noise accelerates the decoherence of quantum states and severely limits the transmission distance in practical continuous-variable quantum state transmission. To address the issue of channel noise in metropolitan quantum fiber-optic links, we propose a scheme called dual channel transferring after interference. This scheme exhibits immunity to additional channel noise while maintaining sufficient communication capacity. Based on this scheme, we experimentally achieve the transmission of a −5.9-dB squeezed state at 1.3 µm through 3 km of optical fiber. We obtain a −3.2-dB output squeezed state and demonstrate that this decrease is solely attributable to channel loss, independent of channel noise. Incidentally, we achieve an improved measurement sensitivity of guided acoustic-wave Brillouin scattering noise in a fiber channel exploiting squeezed light. In addition, beyond its simplic ity of installation and ease of operation, this approach also offers the highest transmission capacity compared with the existing QIT technologies. Our scheme is suitable for almost all modulation-free continuous-variable quantum information protocols, such as quantum secret sharing, quantum entangle ment swapping, and some quantum key distribution schemes with entangled states, as well as participating in the construction of future quantum networks.