Response Function of Homodyne Wavelength Difference Stabilization

We measured the response function at wavelengths of 1540 nm and 1560 nm of an 8-m homodyne interferometer to modulations of the repetition rate and carrier-envelope offset frequency (f ceo ) of an optical frequency comb (OFC). It is known that subtracting the response at one wavelength from the other generates an error signal free of f ceo noise, forming a wavelength difference stabilization (WDS) interferometer that may stabilize non-octave-spanning OFCs. We calculate the WDS response function from our data, and find that while the sensitivity is expected to match a heterodyne system, changes in the response function of a homodyne WDS interferometer due to large-scale drifts of f ceo pose a challenge to robustly stabilize an OFC.