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

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.