Narrow-Linewidth 1.5 μm Nd:YLF-YVO4 Intracavity Raman Laser

We demonstrate a Nd : YLF-YVO₄ intracavity Raman laser in the 1.5 μm eye-safe region. The fundamental wave at 1314 nm from the end-pumped Nd :YLF is down-converted to 1488 nm, utilizing the 890 cm⁻¹ Raman shift of an YVO₄ laser crystal. We use two etalons in the fundamental cavity and Stokes cavity, respectively, to suppress their spectral line width. Under a diode pump power of 43 W at 806 nm, we obtain an average Stokes output power of 3.75 W at an acousto-optic Q-switched pulse repetition frequency of 20 kHz, corresponding to an optical efficiency of 8.7%. With the etalons used, the spectral line width of the Stokes laser is narrowed from over 0.2 to 0.04 nm. The beam quality factor of the eye-safe Stokes output is measured to be 1.12 and 1.19 in the x and y directions, respectively.