Application note: Ultra-low-noise frequency comb offset stabilization

Summary: The Octave Photonics Comb-Offset-Stabilization Module (COSMO) provides a compact method to detect the carrier-envelope-offset frequency (fCEO) of a laser frequency comb. To assess the stability of the locked fCEO, we use one COSMO to measure the fCEO of an Ultra-Low-Noise (ULN) Frequency Comb from Menlo Systems (FC1500-250-ULN) and verify the fidelity of the phase-lock loop using a second COSMO that is outside the feedback loop. After measuring operation for more than 12 hours, we find that the signals from the two COSMO units agree to better than 1e-17 at 1 second and better than 1e-20 at 1,000 seconds. This level of performance is compatible with the most demanding applications.

Figure. Stabilization and out-of-loop verification of fCEO using the COSMO. a) The unlocked fCEO recorded with the COSMO has a high signal-to-noise ratio, enabling tight locking of fCEO. b) The f­CEO frequencies recorded by the two COSMOs show nearly identical stability over the course of 13-hour period. c) the modified Allan deviation shows that the ­fCEO of the comb has been stabilized to a level compatible with ultra-high-stability measurements of optical clocks.

Read more in our Application Note.