Tunable and Linewidth-Reduced Laser Diode Stack for Rubidium Laser Pumping

Linewidth of a laser diode stack with 5 bar is reduced to 0.2 nm from 1.8 nm through the use of an external volume Bragg grating (VBG) cavity. The temperature of the VBG is controlled efficiently to make the central wavelength tunable. The linewidth changes little in the wavelength-tuning experiments. Since the tunable range covers the rubidium D2 absorption line, the stack can be used to pump the rubidium laser efficiently.