Frequency-stabilized laser diode based on the saturated absorption spectrum of Cs D₂ line

Laser diode were easily affected by temperature, vibration and other external factors during free-running operation, and the frequency stability of the output laser was difficult to meet the technical requirements of the fields such as quantum precision measurement, high-precision spectroscopy and laser communication. In order to obtain output laser with stable frequency, a frequency-stabilized laser diode was designed, which was constructed based on the ultra precision energy level structure of the D₂ transition line of ¹³³Cs atoms and the principle of saturated absorption. The atomic transitionline of $\left|6^2 \mathrm{~S}_{1 / 2}, F=4\right\rangle \rightarrow\left|6^2 \mathrm{P}_{3 / 2}, F^{\prime}=5\right\rangle$ was taken as the reference standard of the frequency locked loop (FLL). The results show that, the out-put laser frequency was stabilized by feedback control method. The frequency stability is measured to be 3.88×10^-12 at the integration time of 1 s, and the lowest frequency stability is 1.70×10^-12 at the integration time of 16 s. The long-term frequency fluctuation of 12 h is less than 140 kHz measured from the beat frequency signal. The linewidth is 438.41 kHz@10 μs. The responding rms power stability is 6.11×10^-4.The volume of the whole device is 9×10³ cm³. The combination of saturated absorption spectroscopy and feedback control can significantly reduce the frequency fluctuation of free-running semiconductor lasers. The laser has good performance in some key indicators such as frequency stabilization. It has been miniaturized, which makes it easy to move and maintain. And it operates stably for a long time and is capable of meeting the technical requirements for frequency-locked laser light sources in applications such as quantum measurements.