Abstract

The 1.06-µm Nd transition in co-doped Cr, Nd:Gd₃Sc₂Ga₃O₁₂ (Cr,Nd:GSGG) is shown to produce efficient, low threshold laser operation when pumped with visible laser diodes at 670 nm. Population of the upper laser level occurs by rapid and efficient energy transfer from the Cr^{3+ 4}T₂ state to the Nd ⁴F_3/2 state. Since the Cr³⁺ absorption is quite broad, laser efficiency is insensitive to pump wavelength over the range of wavelengths accessible to the AlGaInP laser diodes. Consequently thermal control of the diode wavelength is unnecessary. Laser threshold powers were measured to be wavelength independent over the range of 610–680 nm when pumped with a dye laser. Diode pump power levels as high as 300 mW cw and 1 W long-pulse were used. Two Cr³⁺ ion densities were used: 1 × 10²⁰ cm^-3 and 2 × 10²⁰ cm^-3. The higher doped rod provided the best results. The lowest threshold power measured was 0.94 mW and the highest output powers obtained were 43 mW cw and 173 mW pulsed. The best slope efficiency obtained was 42.2%. This is 78% of the slope efficiency calculated by multiplying the quantum defect by the measured Cr-to-Nd excitation transfer efficiency. Measured losses were 0.4% cm^-1.

© 1991 Optical Society of America