Imitrines. II. Lasers utilizing solutions of imitrine 1 and imitrine 3 compounds emitting in the 475-575 nm range

An investigation was made of the dynamics of laser action in ethanol solutions of imitrine 1 and imitrine 3 pumped by the third (355 nm) and fourth harmonics (266 nm) of a neodymium laser. At high pump intensities, increased absorption was observed in imitrine 1, accompanied by an increase in the fluorescence intensity. Estimates were obtained of the cross sections for induced absorption at the pump and lasing wavelengths. Dependences of the lasing energy on the reflection of the exit mirror were used to estimate the gain $g_0$ and losses $\alpha_0$ in the medium. It is shown that in imitrine 3 the ratio $g_0/\alpha_0>10^3$ is found. The efficiency of laser action in imitrine 1 exceeds 10 procent and that in imitrine 3 exceeds 20 procent.