マイクロプロセッサ制御による内部鏡He-Neレーザーの周波数安定化

抄録

Simultaneous stabilization of the amplitude and frequency of a two-mode internal-mirror He-Ne laser (λ=633 nm) using a microprocessor controller is reported. The intensity difference between two orthgonally-polarized axial modes normalized by the total intensity is caluculated as a controlled signal. The cavity length is controlled by manipulating the current of a heater wound around the laser tube according to digital PID or I-PD algorithms so that the controlled signal coincides with a reference signal. By adjusting the reference signal, stabilized laser frequency can be tuned within ±300 MHz around the mean frequency of the atomic resonance frequencies of ²⁰Ne and ²²Ne. Frequency stability estimated by the error between the controlled and reference signals is better than 3×10^-8 over a period of 30 minutes. Beat frequency fluctuations between two stabiliezed lasers over a 8 minutes are in the range 1×10^-8 to 2×10^-8 depending on the selected direction of polarization.