Photocurrent Spectrum and Photoelectron Counts Produced by a Gas Laser

The anode-current spectrum of a photomultiplier illuminated by light of time-varying intensity is obtained theoretically. The moments of the photoelectron counts under the same conditions are derived. The expressions are evaluated for the case of light emitted from a laser oscillator by using a semiclassical theory of the Van der Pol oscillator. The theoretical predictions are compared with experiments in which the spectrum of the photomultiplier was observed in the range 0-17 Mc/sec and counts were recorded for counting intervals in the range between ${10}^{-6\mathrm{}}$ and ${10}^{-1\mathrm{}}$ sec. The three lowest order factorial moments were evaluated as functions of $T$ and compared with theory. The spectral data are used to predict the counting data and a comparison is made. The signal-to-noise ratio of the two types of experiments is evaluated and found to be comparable.