Downsampling of optical frequency combs for carrier-envelope offset frequency detection

摘要

We explore downsampling of optical frequency combs by way of pulse gating forefficient spectral broadening and f-2f interferometry. We downsample a 250 MHzrepetition-rate comb to 25 MHz, thereby enabling detection of the comb'scarrier-envelope offset frequency. Pulse gating can both increase timing jitterof the comb's pulse train and induce spurious frequency offsets of the comb'sspectrum. To investigate these effects, we characterize the phase-noisespectrum of the downsampled comb, determine the effects of timing jitterdeliberately imposed on the pulse gate, and demonstrate the null frequencyshift of the comb's optical spectrum to the level of several microhertz.