Delayed-self-heterodyne measurement of laser frequency fluctuations

The two-sample (or Allan) variance of frequency fluctuations was used for laser frequency-noise characterization at Fourier frequencies below 1 MHz. The delayed self-heterodyne technique was used for the variance measurement. Analytical calculations ensure that just twice the variance values were observed at tau <0.3 tau /sub d/, where tau is the averaging time for the frequency measurement and tau /sub d/ is the delay time. The variance measurements of 1.5- mu m distributed Bragg reflector and distributed feedback laser diodes were demonstrated at 6.0*10/sup -7/>