CAVITY EQUATIONS FOR A LASER WITH AN EXTERNALLY INJECTED SIGNAL

We extend the cavity equations of motion for lasers with arbitrary out put coupling [Appl. Phys. Lett. 36, 412 (1980)] to include an external ly injected signal. The external signal is initially introduced into t he cavity through the output coupler and enters the formulation throug h the boundary condition on the cavity electric field. A transformatio n is performed so that the injected signal is eliminated from the boun dary condition and replaced by a driving-polarization term in the equa tions of motion for the cavity field that develops as a result of lase r gain. We illustrate the use of this new formulation by applying it t o an injection-seeded, gain-switched, standing-wave pulsed oscillator. The intracavity intensities as functions of axial position and time a re compared for single-frequency and multiple-frequency operation.