Lasers with nonlinear active media

A theoretical investigation is made of the main relationships governing single-mode cw intracavity generation of the second optical harmonic in a laser with a nonlinear active medium which combines the functions of stimulated emission and frequency doubling by the superposition of laser and nonlinear optical processes in the nonlinear active medium. The basic equations determining the generation intensity are derived and solved analytically near the generation threshold and numerically outside the thresh old range. Analyses are made of travelling and standing-wave lasers with radiation coupled out on one and two sides. Investigations are made of cases when the resonator does not emit at the fundamental frequency ω₁ and only the ω ₂=2ω₁ radiation is coupled out or both the ω₁ and ω ₂ waves are coupled out simultaneously. A study is also made of some characteristics of the propagation of coupled ω_1,2 waves in a semiinfinite nonlinear active medium, in particular, of the stability of the different solutions. An analysis is made of the effect of the main parameters (length of nonlinear active medium, pumping rates and nonlinearities, dissipative losses at the frequencies ω_1,2 and so on) on the generation intensity and choice of optimal conditions. It is shown that optimal values exist for the nonlinear active medium length, pumping, nonlinearity, and other factors.