Laser-diode-pumped tunable solid state laser

Abstract

The first operation of a direct diode-pumped tunable chromium-doped solid state laser is reported. A small alexandrite crystal (Cr:BeAl2O4) was placed in a hemispherical cavity and longitudinally pumped by two 680 nm laser diodes. The threshold pump power was found to be 12 mW using the R1 line at 680.4 nm for the pump transition. A tunable dye laser was employed to probe the dependence of the threshold power on wavelength over the broad absorption band to the blue of the R lines, and pump threshold powers ranging from 15 mW at 630 nm to 55 mW at 670 nm were recorded. With no dispersive element in the cavity the output was broadband and its spectral width depended on pump power. At threshold, the measured bandwidth was 2.1 nm and increased to 3.1 nm at a pump level approximately 10 times threshold. The slope efficiency for diode pumping was measured to be 25 percent.