Novel method of estimation flicker frequency noise in lasers

A simple method is proposed for the precise measurement of flicker (1/f) frequency noise in lasers. The method is based on measurement of the Allan variance of beat signals produced by delayed self-heterodyning. A simple relation between measured variance and frequency-noise spectrum is derived analytically. Measurement on a 1.5- mu m semiconductor laser diode is presented. It is pointed out that since the method possesses the great advantage of insensitivity to optical power fluctuations, it can be widely used for precisely testing laser frequency quality.>