Abstract

Although the Nd:YAG laser operated on the ⁴F_3/2 – ⁴I_11/2 transition at 1.06 μm is one of the most highly developed solid-state lasers, the relaxation rate of the terminal ⁴I_11/2 level is not well established. The reported lifetimes range from 10 ns to 1 μs (1-4). Most modeling of this system assumes that the lifetime of the ⁴I_11/2 level τ₁ is short compared to that of the laser cavity lifetime τ_c. For Q-switched Nd:YAG lasers with relatively large outcouplings per pass and pulsewidths of ~10 ns, a value for t₁ at the lower end of the reported range would make this assumption questionable. Fan (5) recently reported on a study of the effect of a finite τ₁ on the extraction efficiency and pulse shape in Q-switched Nd:YAG lasers. For τ_c ≫ τ₁, he found an extraction efficiency that was 68 percent of that expected for τ_c ≪ τ₁. In this work we report measurements of the time dependent gain of a Q-switched Nd:YAG laser which, when coupled with modeling results, allow us to place an upper limit of 9 ns on τ₁.

© 1990 Optical Society of America