THz oscillators generated via frequency-multiplication of microwaves are
facing difficulty in achieving low phase noise. Photonics-based techniques, in
which optical two tones are translated to a THz wave through opto-electronic
conversion, are promising if the relative phase noise between the two tones is
well suppressed. Here, a THz (≈ 560 GHz) wave with an unprecedented
phase noise is provided by a frequency-stabilized, dissipative Kerr
microresonator soliton comb. The repetition frequency of the comb is stabilized
to a long fiber in a two-wavelength delayed self-heterodyne interferometer,
significantly reducing the phase noise of the THz wave. A new measurement
technique to characterize the phase noise of the THz wave beyond the limit of a
frequency-multiplied microwave is also demonstrated, showing the superior phase
noise of the THz wave to any other THz oscillators (> 300 GHz)