COMPUTER-CONTROLLED NARROW-LINEWIDTH AND FREQUENCY-STABILIZED ALGAAS LASER SYSTEM WITH UNMODULATED OUTPUT

A narrow-linewidth semiconductor laser system at 780 nm wavelength was developed, with frequency locked to the saturation absorption resonan ce frerquency of rubidium (Rb-87). Optical feedback from an external F abry-Perot cavity was employed to reduce the linewidth of the laser. T he third derivative of the saturated absorption spectrum in Rb-87 was used as a frequency demodulator for frequency locking, for which the Z eeman modulation was employed to keep the output power and frequency u nmodulated. The minimum of the square root of the Allan variance was 2 .1 X 10(-12) at the integration time of 300 s. The full linewidth at h alf maximum of the field spectrum was measured to be narrower than 170 kHz. A computer-control program was developed for automatic frequency locking to the Rb-87 line.