A proposed FM phototube for demodulating microwave-frequency-modulated light signals

A microwave phototube for demodulating frequency-modulated light signals is proposed. The demodulation is based upon the conversion of the frequency-modulated light into space-modulated light via an optical dispersing element. This space-modulated light is then incident on a photocathode where it is the source of transverse electron beam waves. A complete spectral analysis of the demodulation process is presented. It is shown that a quasi-steady-state viewpoint, i. e., that of an optical signal with slowly varying frequency is permissible only if the optical resolution is sufficiently low. Design parameters for a phototube based on the use of a Michelson echelon are presented. A related scheme employing a Fabry-Perot etalon is also discussed.