Abstract
We show a unique dual-wavelength external-cavity laser diode with frequency tracking capability and obtain a stable beat frequency between the dual-wavelength output. By using a Fabry-Perot interferometer as the frequency discriminator and the time-gating technique in a servo loop, the peak-to-peak frequency fluctuations were stabilized, with respect to the Fabry-Perot cavity, to 86 kHz in the dual-wavelength output at 802.5 and 804.5 nm, and to 17 kHz in their 0.9 THz beat signal. Similar performance was achieved for tuning of the dual wavelength separation ranging from 0.2 to 4 nm.