Spin saturation and pump depletion in continuous spin-flip Raman oscillation

A saturation model of stimulated Raman scattering, of general applicability, is put forward. The model is developed with reference to spin-flip electronic Raman scattering in InSb, where the number of excitations available for Raman scattering may be small by comparison with the incident photon numbers. A rate equation technique is used to evaluate the steady-state Stokes intensity and output powers for a Gaussian pump beam. The model is extended to take account of pump depletion and the relative importance of depletion, and saturation in limiting the conversion efficiency under different conditions is brought out. By comparison with continuous wave spin-flip measurements, values are obtained for the spin-relaxation time (τ
s
) associated with spin reversal in InSb. For 10
¹⁶
free carriers per cubic centimeter at 36 kG,
\tau_{s} \sim 12
ns and for 10
¹⁵
cm
^-3
at 16.9 kG,
\tau_{s} \sim 1.3
ns.