Upconversion laser action at 469.7 and 560.6 nm in Er:YLiF₄

Abstract

CW upconversion laser action in Er:YLiF4 on transitions in the green (560.6-nm) and blue (469.7-nm) spectral regions is reported. The experiments were carried out using 3-mm-long crystals of 1% Er:YLiF4 with mirror coatings directly applied to spherically polished (R = 2-cm) faces and an output coupling of 1%. Lasing at 560.6 nm was observed by exciting either at 797.0 nm or into the 4I9/2 level with a dye laser at 797.0 nm or into 4I11/2 using a Ti:sapphire laser at 968.9 nm. Laser action at 469.7 nm was observed using another crystal with coatings appropriate for this wavelength. Efficient laser action has been observed with very modest pump powers. The pump wavelengths and powers used are accessible with III-V semiconductor diode lasers.