Operating a laser diode in an external cavity, which provides frequency-selective feedback, is a very effective method to tune the laser frequency to a range far from its free running frequency. For the Ca atomic Ramsey spectroscopy experiment, we have constructed a 657-nm laser system based on the Littman-Metcalf configuration with a 660-nm commercial laser diode. Continuously 10-GHz tuning range was achieved with about 100-kHz spectral linewidth, measured with beat-note spectrum of two identical laser systems.
© 2005 Chinese Optics Letters
Desheng Lu, Kaikai Huang, Fengzhi Wang, and Donghai Yang, "External cavity diode laser around 657 nm," Chin. Opt. Lett. 1, 656-657 (2003)