The physical properties of CVD diamond make it excellent medium for high average power Raman laser generation. We have been thinking of using diamond to generate sodium guide star lasers. In the past few years, we have been cooperating with Prof. Mildren’ group at Macquarie Universty on fiber laser pumped diamond Raman lasers. A particular interest is to develop a new diamond Raman guide star laser technology, an important alternative to the already developed fiber Raman technology. Recently, we have made breakthough in this topic, thanks to the hard work of Mr. Xuezong Yang, who is a Ph.D. student jointly suported by UCAS and MU. The results was published on Optics Letters：
Xuezong Yang, Ondrej Kitzler, David J. Spence, Zhenxu Bai, Yan Feng, and Richard P. Mildren, “Diamond sodium guide star laser,” Opt. Lett. 45, 1898-1901 (2020)
Abstract: Laser guide stars based on the mesospheric sodium layer are becoming increasingly important for applications that require correction of atmospheric scintillation effects. Despite several laser approaches being investigated to date, there remains great interest in developing lasers with the necessary power and spectral characteristics needed for brighter single or multiple guide stars. Here we propose and demonstrate a novel, to the best of our knowledge, approach based on a diamond Raman laser with intracavity Type I second-harmonic generation pumped using a 1018.4 nm fiber laser. A first demonstration with output power of 22 W at 589 nm was obtained at 18.6% efficiency from the laser diode. The laser operates in a single longitudinal mode (SLM) with a measured linewidth of less than 8.5 MHz. The SLM operation is a result of the strong mode competition arising from the combination of a spatial-hole-burning-free gain mechanism in the diamond and the role of sum frequency mixing in the harmonic crystal. Continuous tuning through the Na D line resonance is achieved by cavity length control, and broader tuning is obtained via the tuning of the pump wavelength. We show that the concept is well suited to achieve much higher power and for temporal formats of interest for advanced concepts such as time-gating and Larmor frequency enhancement.