5.1 - Use of an oscillating laser as a heterodyne receiver preamplifier

In this paper the results of a study of the amplification characteristics of lasers for signals injected near their frequencies of oscillation are reported. An approximate theoretical treatment is given which indicates that substantial amplification will occur under conditions for which the anisotropy of the laser cavity is small, the polarization state of the injected signal is orthogonal to that of the primary oscillation, and the two signals are critically coupled. For like polarization of these signals, postive amplification occurs only for substantially reduced laser excitation or increased cavity loss. The experimental observations are in qualitative agreement with the theoretical predictions with gains as high as 600 having been observed for orthogonal polarizations near critical coupling. The optical bandwidth appears to be at least several MHz.