Pascal P. Del'Haye, Scott B. Papp, Scott A. Diddams
Optical frequency combs based on mode-locked lasers have proven to be invaluable tools for a wide range of applications in precision spectroscopy and metrology. Recently, a novel principle of optical frequency comb generation in whispering gallery mode microresonators has been developed, representing a promising route towards chip-level integration and out-of-the-lab use of 'microcombs.' Presently, two distinct families of microcombs have been demonstrated: those with an octave-spanning spectrum which is critical for self-referenced stabilization and others with narrow mode spacing which is important for direct electronic detection and frequency stabilization. However, to date it has not been possible to achieve these two key-requirements simultaneously, as will be critical for most microcomb applications. Here, we present a novel approach to solve this problem by interleaving an electro-optic comb with the spectrum from a parametric microcomb. This allows, for the first time, direct control and stabilization of a microcomb spectrum with large mode spacing (>140 GHz) without the need for an additional mode-locked laser frequency comb. The attained relative stability of the microcomb comb spacing is 10-15 within 1 second, which is a new record compared to previously reported values.
Eletro-Optic Modulation, Four-wave mixing, Microresonator, Optical Frequency Comb, Stabilization