Measurement of nonlinear frequency chirp of Q-switched ruby laser

The frequency chirp of a Q-switched ruby laser is investigated with two interference experiments: holography of a rotating object and measurement of time coherence. Nonlinearity of the frequency chirp markedly affects both interference experiments for large time differences between the two beams, which enable us to determine the nonlinear frequency chirp, that is, chirp rate and time. A hyperbolic tangent function provides a better approximation of the frequency chirp than the linear function generally used. In this experiment the chirp time was 1.0-1.5 times as long as the half-intensity width of the pulse.