Frequency Measurement for Laser Stabilization Based on the Beat-sampling Method.

Frequency measurement is one of the important parts of the laser frequency stabilization system. In this paper, a novel high-precision frequency measurement technique based on the beat-sampling method is presented. The input signal is beat sampled with a 1-bit ADC to reduce the frequency, thereby improving measurement accuracy within the same measurement time. Two sampling sub-channels are designed to confirm the exact value of the input signal frequency. Besides, a prototype is implemented to verify the proposed method. The prototype is a digital control system supported by a field programmable gate array (FPGA). Compared to the traditional beat-frequency circuits, the prototype consists of simpler circuits and enables a higher grade of flexibility. The results obtained demonstrated that signals with a frequency of 100 MHz could be measured within 1s at an accuracy of mHz.