Demodulation of phase-modulated light using birefringent crystals

The application of birefringent crystals to accomplish the demodulation of phase-modulated light is considered. A particular combination of crystals and a polarization insensitive photodetector is termed a birefringent demodulator, and shown to have the properties that it will 1) convert a phase-modulated light signal into an amplitude-modulated light signal and subsequently detect it in a nearly lossless manner, and 2) simultaneously suppress or balance out an incident amplitude-modulated light signal. A time domain version of the "Jones Calculus" is formulated and used to analyze the demodulator. Conversion efficiency, suppression efficiency, and bandwidth are considered. Experimental results demonstrating PM to AM conversion and AM suppression at microwave modulation frequencies between 2 and 12 Gc are given.