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Single-frequency (SF) lasers in the visible spectral region are usually obtained through an indirect method, i.e., frequency doubling of near-infrared SF lasers. In this work, we report on the direct generation of a high-power continuous-wave (CW) SF laser in red based on a diode-pumped Pr:LiYF 4 (YLF) ring cavity technology. A maximum output power is scaled to 3.98 W at 640 nm with a linewidth of about 17.2 MHz and a power stability of 0.6%. Moreover, by inserting a LBO crystal into the ring cavity for intracavity frequency doubling of the 640 nm SF laser, we have also successfully demonstrated an ultraviolet (UV) SF laser at 320 nm, for the first time to the best of our knowledge, with a maximum power of 670 mW. This work provides a promising route for the development of simple, compact, and high-power SF lasers operating in visible and UV spectral regions.

Using a CZ-grown a-cut Pr:YLF crystal as laser gain medium after processing it into crystal fiber, we have demonstrated real Pr 3+ -doped single-crystal fiber lasers for the first time to the best of our knowledge. This Pr 3+ crystal fiber has absorbed up to 20.4 W of pump power, which is the highest absorbed power among Pr 3+ lasers. For two representative laser emissions at about 639 nm and 607 nm, we have achieved maximum output powers of 5.45 W and 3.04 W, respectively. Output powers of the two lasers show very good linearities, which indicate that the present output powers are only limited by the available pump power. Both laser emissions have exhibited near diffraction-limited beam qualities. This proposal has provided a good and feasible route for the development of compact, high-power, and high-brightness all-solid-state Pr 3+ visible lasers via crystal fiber.