Threshold-less and Flexibly Tunable Frequency Comb via Floquet Engineering

Frequency combs have revolutionized communication, metrology and spectroscopy. Numerous efforts have been dedicated to developing integrated combs, predominantly relying on Pockels or Kerr mechanisms. In this work, we propose and demonstrate a new type of frequency comb- Floquet cavity frequency comb -that does not rely on intrinsic material non-linearity. By periodically modulating the resonance frequency of a cavity, a Floquet cavity with multiple equally spaced frequency components is created. The pump tone interacts with the pre-modulated cavity, generating the output frequency comb. This approach offers a flexible tuning range and operates in a threshold-less manner, obviating the need to overcome nonlinear initiation threshold. We implement this on a microwave cavity optomechanical system on-chip. Compared to Kerr optomechanical combs, this approach efficiently generates comb with pump signal far from the cavity's intrinsic frequency, and the power required for detection is reduced by approximately a factor of \(10^6\), providing a promising platform for frequency comb generation.