Here we describe advances in laser frequency microcombs in dispersion-engineered microresonators. We examine the phase/frequency-noise and jitter characteristics of microcomb states. When referenced to high-purity sources, the microcomb preserves tooth-to-tooth relative frequency stabilization to a 50 mHz and 2.7×10−16 uncertainty. We also examine the real-time transition dynamics and stability of these dispersion-engineered microcombs.
We further describe advances in coherent THz-mmWave radiation generation via frequency microcombs, with 2.8-octaves (330 GHz to 2.3 THz) tunability. With photomixers from Jarrahi group at UCLA, coherent sub-100-Hz linewidth radiation is demonstrated with 10-15 residual frequency instability, supporting applications in high-frequency metrology, sensing, imaging and communications.
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