Phase-modulated conjugate-wave generation in ruby

Phase-modulation experiments have been performed in a degenerate four-wave mixing geometry in ruby at modulation rates faster than the relaxation rate of the ruby. The dc value of the conjugate wave signal is measured as a function of modulation amplitude and type; the results are explainable in terms of a blurred-hologram analogy. The time-dependent behavior of the conjugate-wave signal shows frequency doubling, which is also explained in terms of a real-time hologram model.