Autocorrelator for the measurement of a quasi-continuous-wave laser beam sinusoidally modulated at 17 THz

The development of an autocorrelator, using a photomultiplier as a nonlinear optical detector, for the measurement of a quasicontinuous- wave laser beam in the milliwatt range, is described. The contribution of the two-photon absorption relative to the onephoton absorption was investigated for the Sb–Cs photocathode used in the photomultiplier by means of the Z-scan method. This autocorrelator was applied to the measurement of the intensity of a laser beam sinusoidally modulated in the tetrahertz range.