Widely Tunable External Cavity Laser Diode Injection Locked to an Optical Frequency Comb

We report an ultrastable external cavity laser diode (ECLD) that can be selectively injection locked to an optical frequency comb (OFC) generated by acetylene stabilized laser (ASL) seeding. The carrier envelope offset (position) and repetition rate (mode spacing) of the OFC, which functions as the master oscillator, was stabilized to the ASL (1.1 × 10^-12 at 1 s) and H-maser (2 × 10^-13 at 1 s), respectively. The ECLD can be tuned over 70 nm in the 1.5-μm region and can be discretely locked to the comb modes with 25-GHz spacing over a 10-THz span. The frequency stability of the ECLD injection locked to the OFC reached as high as 1.1 × 10^-12 for 1-s averaging time.