300 GHz wave with attosecond-level timing noise

Optical frequency division (OFD) via optical frequency combs (OFC) has enabled a leap in microwave metrology leading to noise performance never explored before. Extending the method to millimeter-wave (mmW) and terahertz (THz)-wave domain is of great interest. Dissipative Kerr solitons (DKSs) in integrated photonic chips offer a unique feature of delivering OFCs with ultrahigh repetition rates from 10 GHz to 1 THz making them relevant gears to perform OFD in the mmW and THz-wave domain. We experimentally demonstrate OFD of an optically-carried 3.6 THz reference down to 300 GHz through a DKS, photodetected with an ultrafast uni-traveling-carrier photodiode (UTC-PD). A new measurement system, based on the characterization of a microwave reference phase-locked to the 300 GHz signal under test, yields attosecond-level timing noise sensitivity, leveraging conventional technical limitations. This work places DKSs as a leading technology in the mmW and THz-wave field promising breakthroughs in fundamental and civilian applications.