Method of phase locking frequency stabilization for diode lasers by F-P optical cavity

Aiming at the issue of the frequency instability of emergent light from diode lasers in Littman configuration, a stabilization method combined F-P cavity with phase-locked amplifier is proposed. The laser frequency is stabilized to the resonance frequency corresponding to the average cavity length of a F-P cavity. A function generator is used to drive the F-P cavity according to the sinusoidal signal, and a photoelectric detector is used to transform optical signals passing through F-P optical cavity into electrical signals. The electrical signals frequency mix with drive signals from function generator and then pass trough low pass filter in the phase-locked amplifier to get optical cavity resonance signal phase error. The signal is given back to laser by PID controller to stable optical frequency through the feedback selection of internal current and external cavity PZT driving voltage. We theoretically deduce the correlation between optical cavity resonance signal phase error and the laser wavelength, and then choose the standard deviation of the F-P optical cavity transmission peak time interval value τ as a frequency stability evaluation index. Experiments show that the stability of external cavity semiconductor laser frequency is improved by 80% via feedback selection of external cavity PZT driving voltage. This method is simple and efficient to be applied to different wavelengths and longtime laser frequency stabilization.