Broadband Millimetre Wave Comb Generation via Laser-Cavity Soliton Microcombs

Critical applications such as ultra-fast communication and precision radar demand sources capable of delivering low-jitter, highly stable signals in the millimetre wave range. Optical frequency combs in microresonators, or microcombs, have emerged as important sources for distributing metrological references in the 100 GHz to THz range [1]–[4]. We present a millimetre wave comb generated directly from a laser cavity-soliton (LCS) microcomb [5]. This system leverages the stability, high conversion efficiency, and compactness of LCS microcombs centred at wavelength <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\lambda=1545 \text{nm}$</tex>, achieving pulsed millimetre radiation at the repetition rate of the microcomb (50 GHz) with a spectrum reaching 650 GHz. Our approach provides low-jitter (less than 1 fs from a locked LCS comb) generation, crucial for high-speed data transmission, real-time diagnostics, and advanced spectroscopy. The emission is achieved using photoconductive antennas and operating our diagnostic in a time- domain spectroscopy configuration, typical of terahertz (THz) generation systems. By manipulating soliton states, we demonstrate control over the phase and amplitude of the millimetre wave comb. The radiation can be obtained from the system when operated without external amplification, with half of the comb power fed to the emitter and half to the diagnostic, respectively. These advancements position the LCS-based millimetre wave comb as a versatile and scalable platform for future THz-integrated systems. This work opens new possibilities for ultra-fast communication, precision metrology, and on-chip spectroscopic applications and clock dissemination.