Heterodyne detection with an injection laser. II. Signal-to-noise ratio

For pt.I see ibid., vol.26, p.85-93 (1990). In part I a theory of the conversion efficiency of the self-heterodyne laser detector that was first described by R.F. Kazarinov and R.A. Suris (1974) was presented. In this device a light signal is passed into the resonant cavity of an actively oscillating injection laser, causing an electrical signal at the difference frequency between laser and signal to flow through the wire supplying the DC bias to the laser. An expression is derived for the signal-to-noise ratio of the self-heterodyne laser detector. The result shows that in the limit of ideal operation (complete population inversion and no internal losses) the signal-to-noise ratio of the self-heterodyne laser detector reaches one-half of the quantum noise limit