Stepped-Frequency THz-wave Signal Generation From a Kerr Microresonator Soliton Comb

Abstract: Optically generated terahertz (THz) oscillators have garnered considerable attention in recent years due to their potential for wide tunability and low phase noise. Here, for the first time, a dissipative Kerr microresonator soliton comb (DKS), which is inherently in a low noise state, is utilized to produce a stepped-frequency THz signal ($\approx$ 280 GHz). The frequency of one comb mode from a DKS is scanned through an optical-recirculating frequency-shifting loop (ORFSL) which induces a predetermined frequency step onto the carrier frequency. The scanned signal is subsequently heterodyned with an adjacent comb mode, generating a THz signal in a frequency range that is determined by the repetition frequency of the DKS. The proposed method is proved by proof-of-concept experiments with MHz level electronics, showing a bandwidth of 4.15 GHz with a frequency step of 83 MHz and a period of 16 $\mu$s.