Mapping ultrafast timing jitter in dispersion-managed 89 GHz frequency microcombs via self-heterodyne linear interferometry

TL;DR

This paper demonstrates precise characterization of ultrafast timing jitter in 89 GHz dispersion-managed microcombs using self-heterodyne interferometry, revealing near-quantum-limited noise performance across different mode-locking states.

Contribution

It introduces a high-resolution self-heterodyne interferometric method to map timing jitter in microcombs, achieving near-quantum-limited noise measurements at 89 GHz.

Findings

Achieved near-shot-noise-limited relative intensity noise of -153.2 dB/Hz.

Measured quantum-noise-limited timing jitter of 0.4 as^2/Hz at 100 kHz offset.

Demonstrated integrated timing jitter of 1.7 fs from 10 kHz to 1 MHz.

Abstract

Laser frequency microcombs provide equidistant coherent frequency markers over a broad spectrum, enabling new frontiers in chip-scale frequency metrology, laser spectroscopy, dense optical communications, precision distance metrology and astronomy. Here we demonstrate thermally stabilized frequency microcomb formation in dispersion-managed microresonators at the different mode-locking states featured with the negligible center frequency shift and broad frequency bandwidth. Subsequently, femtosecond timing jitter in the microcombs are characterized, supported by precision metrology on the timing phase, relative intensity noise and instantaneous linewidth. We contrast the fundamental noise for a range of 89 GHz microcomb states, from soliton crystals to multiple solitons and single-soliton regimes, determined by pump-resonance detuning. For the single-soliton state, we report a close-to-shot-noise-limited relative intensity noise of -153.2 dB/Hz and a quantum-noise-limited timing jitter power spectral density of 0.4 as2/Hz, at 100 kHz offset frequency. This is enabled by a self-heterodyne linear interferometer with 94.2 zs/Hz1/2 timing resolution, 50.6 mHz/Hz1/2 RF frequency resolution, and 6.7 uV/Hz frequency discrimination sensitivity. We achieve an integrated timing jitter at 1.7 fs, integrated from 10 kHz to 1 MHz. Measuring and understanding the fundamental noise parameters in these high-clock-rate frequency microcombs are essential to advance soliton physics and precision microwave-optical clockwork.