Abstract

Visible all-solid-state lasers have been realized mainly by frequency doubling of IR-lasers or up-conversion pumping schemes. In those schemes, the electric-optical conversion efficiency was lower especially in CW mode. Trivalent praseodymium doped fluoride crystals, e.g., LiYF₄, have been receiving much attentions as a laser material which can directly producing visible wavelength light because their energy level manifolds allow transitions in blue, green, orange and red regions as shown Fig.1. A CW Pr³⁺:LiYF₄ laser was demonstrated using an Ar ion laser[1], a frequency-doubled Nd:YAG laser, or a 442 nm GaN laser diode[2]. However, due to slight difference in the absorption peak from those pumping laser sources, highly doped and longer materials were required. Thus, concentration quenching and optical losses impede the efficient operation. The highest laser output of the GaN laser diode pumped Pr³⁺:LiYF₄ laser was as low as 1.5 mW at a slope efficiency of 24 % because the maximum output of the GaN laser diode was a few tens mW [2].

© 2007 IEEE