Abstract

Nd-doped solid-state lasers have been demonstrated in the wavelength region centered about 940 nm, the ⁴F_3/2—⁴l_9/2 transition. Typically it is difficult to achieve oscillation on this transition because the lower laser manifold is also the ground state manifold, and the gain near 1.05 μm; the ⁴F_3/2—⁴l_11/2 transition is higher. The first causes the threshold to be higher because the lower laser level is populated, and the second causes difficulties because of parasitic oscillation of the ⁴F_3/2—⁴l_11/2 transition. However, these difficulties can be overcome; we have demonstrated cw oscillation at 946 nm at room temperature with a threshold of 11 mW of absorbed pump power at 588 nm in Nd:YAG. The slope efficiency is only 3.6%, but the nominal output coupling of 0.3% is below optimum. By cooling the laser from 296 to 256 K, which reduces the lower laser level population, the threshold was reduced to 7 mW. The pump beam was chopped for all these quantitative measurements to reduce effects of heating of the crystal, but true cw oscillation was also demonstrated. While this threshold power is low, further reduction of threshold appears possible by optimization of the cavity mode volume.

© 1986 Optical Society of America