Quantum Theory of a Raman Laser

The quantum theory of a coherently driven optical cavity with an intracavity Raman active medium is presented. This system is shown to give rise to laser action at the Stokes frequency. A Fokker-Planck equation is derived for the Stokes mode and shown to assume the same form as that for the usual laser. The limiting noise in this Raman laser arose from the spontaneous decay of a pump photon into a Stokes photon and a phonon.