External cavity diode laser at 509 nm for Cs Rydberg atoms

To address the demand for narrow-linewidth, tunable lasers in Cs Rydberg atomic receivers, we have developed a 509 nm ultra-narrow linewidth laser based on the Littrow configuration. The linewidth narrows to 30.0 ± 0.4 kHz, representing a notable improvement compared to previously reported values obtained using the same Littrow configuration. The output power of the grating external cavity diode laser is 5.08 mW under strong feedback conditions. The laser’s continuous mode-hop-free tuning range is enhanced by optimizing the feed-forward technology. Current scanning enables a continuous mode-hop-free tuning range of 152 pm (176 GHz). The laser offers a tuning range of 509 ± 2 nm and achieves a continuous mode-hop-free wavelength tuning of 145 pm (168 GHz) through piezoelectric transducer scanning. Specifically, by implementing direct current modulation of the laser diode, we achieve a frequency sweep rate of up to 57.6 GHz/ms, which satisfies the fast frequency hopping requirements of radar receivers. Over a 2.5 h period, the free-running wavelength fluctuation remains below 1 pm. These results demonstrate that the laser is highly suitable for implementation in Rydberg atomic receivers.