ZHANG Hui¹, CHEN Jiang^2,3, LIU Dan-dan^2,4, RUAN Jun^2,3,4,

REN Zhao-yu¹, ZHANG Shou-gang^2,4

(1. Institute of Photonics & Photon technology, Northwest University, Xi′an 710600, China;

2. National Time Service Center, Chinese Academy of Sciences, Xi′an 710600, China;

3. Graduate University of Chinese Academy of Sciences, Beijing 100039, China;

4. Key Laboratory of Time and Frequency Primary Standard, National Time Service Center,

Chinese Academy of Sciences, Xi′an 710600, China)

Abstract: We report a frequency tunable external-cavity DFB laser, using the feature that the extraordinary refraction index of a liquid crystal variable retarder(LCVR) would change as a function of the voltage applied on the liquid crystal. The output laser linewidth of this LCVR external-cavity diode is 475 kHz, the laser frequency range can span 7 GHz when the bias voltage varies 1.6 V(0.5~2.1 V), covers all the saturated absorption spectroscopy of the Cs D₂ line. Compared with the PZT driven tunable diode laser, frequency tuning with liquid crystal is advantageous regarding the low bias voltage, small retrace error, and high mechanical stability.