CW Gain Characteristics of Linear Optical Amplifiers

The operation of the linear optical amplifier is described in terms of the two mutually orthogonal optical waves in the cavity of a vertical-cavity surface-emitting laser (VCSEL) when operated above threshold. Both photon populations induce stimulated emission from the same quantum-well population and the amplifier gain is constant due to the clamped value of stimulated lifetime (gain) in the VCSEL. An analytical description is developed for both the constant gain region when the VCSEL is above threshold and for the region of gain compression at higher input power. The maximum gain is found to occur at the cavity mode position. Experimental data are found to be well matched by the calculated results.