Abstract

Recently, there has been renewed interest in the development of short wavelength solid state lasers pumped by upconversion mechanisms. Here we report for the first time we believe on cw pumped upconversion lasing of the Tm³⁺ ion at 450.2 and 483.0 nm using two different excitation schemes at temperatures between 20 and 130 K. Pulsed upconversion lasing at 450.2 nm was recently reported in Tm:YLiF₄ using two pulsed dye lasers at 780.8 and 648.8 nm for pumping at liquid-nitrogen temperature.¹ Here we used cw dye lasers of several hundred milliwatts power to excite a. monolithic 3-mm long laser crystal of 1.8% Tm:YLiF₄ with mirror coatings directly applied to the spherically polished (R = 2-cm) faces (1% output coupling). The crystal was mounted with its c-axis perpendicular to the laser axis in a gas flow liquid- helium cryostat where the temperature could be varied between 2 and 300 K.

© 1990 Optical Society of America