Correlated laser spectral and intensity noise in short-path-difference interferometers

A novel technique has been developed for stabilising against drift and vibration the path difference of a Michelson two-path interferometer. The technique has enabled measurements to be made for the first time of semiconductor laser noise around individual interference fringes near to, and including, zero order. Minimum noise was not detected at zero path difference as had been expected: this characteristic may be explained by assuming partial correlation between the source intensity and demodulated spectral noises.