Abstract

Parametric instability induced by the medium saturation in stimulated Raman scattering is investigated theoretically via a generalized detuning (1) where ω_p,s,oare the frequency of the pump, Stokes, and phonon, ${\dot{\varphi }}_{ps}$ is the phase modulation, and the last term is the nonlinear correction of the highly excited anharmonic molecule with an amplitude Q.The steady-state gain and hence the Stokes efficiency, in the presence of the anharmonic term, are governed by a cubic equation of |Q|²which is to be solved from the Bloch and Maxwell equations including the pump depletion. Numerical results are shown for the transition diagram of Stokes efficiency vs input pump intensity at various system conditions at the steady-state. For the transient regime, with pulse duration shorter than the dephasing time, we analyze the temporal profiles of the Stokes and the depleted pump based on a transformed equation which combines Bloch and Maxwell equation as follows: (2) where Tis a nonlinear time, G_sis the steady-state gain, l₀is the input pump intensity, and Uis the real part of the phonon amplitude Q.For an input pulse intensity given by sech²(t/t_p), Eq. (2) is solved numerically to study the transient pulse profiles in the presence of pump depletion and medium saturation.

© 1985 Optical Society of America