The first demonstration of a 639-nm regenerative laser amplifier

High-power picosecond lasers in the visible and ultraviolet wavelength hold a lot of advantages in various applications. The high absorption efficiency in the various metals leads to the higher removal rates, and the shorter pulse widths can suppress thermal influence during the material processing. Recently, the significant progress in the output power of indium gallium nitride (InGaN)-based laser diodes (LDs) has developed the compact high-power lasers which oscillate directly in the visible wavelength. For example, a continuous-wave laser output power of >6.7 W at the fundamental wavelength of 639 nm was reported with a praseodymium-doped LiYF4 crystal (Pr:YLF) [1]. Moreover, mode-locked picosecond lasers were also reported using a SESAM saturable absorber with Pr:YLF lasers [2,3]. Further scaling of visible picosecond laser pulse requires an amplifier, but only few experiments were reported on the visible laser amplifiers [4]. For example, the maximum amplification factor of 10 was demonstrated at 478 nm [5]. In this paper, a 639-nm picosecond-pulse regenerative amplifier using a Pr:YLF crystal is demonstrated for the first time.