Timing jitter characterization of free-running dual-comb laser with sub-attosecond resolution using optical heterodyne detection

TL;DR

This paper introduces a highly sensitive optical heterodyne detection technique for measuring the ultra-low timing jitter of free-running dual-comb lasers with sub-attosecond resolution, enabling advanced optical measurement applications.

Contribution

The authors developed a novel measurement method that can characterize the timing jitter of dual-comb lasers with any repetition rate difference, achieving sub-attosecond resolution.

Findings

Achieved a timing jitter measurement noise floor of 8.0×10⁻⁷ fs²/Hz.

Demonstrated a dual-comb laser with 13 fs rms timing jitter from 100 Hz to 1 MHz.

Validated the technique's capability for free-running dual-comb system characterization.

Abstract

Pulse trains emitted from dual-comb systems are designed to have low relative timing jitter, making them useful for many optical measurement techniques such as optical ranging and spectroscopy. However, the characterization of low-jitter dual-comb systems is challenging because it requires measurement techniques with high sensitivity. Motivated by this challenge, we developed a technique based on an optical heterodyne detection approach for measuring the relative timing jitter of two pulse trains. The method is suitable for dual-comb systems with essentially any repetition rate difference. Furthermore, the proposed approach allows for continuous and precise tracking of the sampling rate. To demonstrate the technique, we perform a detailed characterization of a single-mode-diode pumped $\mathrm{Yb:CaF_2}$ dual-comb laser from a free-running polarization-multiplexed cavity. This new laser produces 115 fs pulses at 160 MHz repetition rate, with 130 mW of average power in each comb. The detection noise floor for the relative timing jitter between the two pulse trains reaches $8.0 \times 10^{-7} \, \mathrm{fs}^2/\mathrm{Hz} \; ( \sim 896 \: \mathrm{zs}/\sqrt{\mathrm{Hz}} )$, and the relative root mean square (rms) timing jitter is 13 fs when integrating from 100 Hz to 1 MHz. This performance indicates that the demonstrated laser is highly compatible with practical dual-comb spectroscopy, ranging, and sampling applications. Furthermore, our results show that the relative timing noise measurement technique can characterize dual-comb systems operating in free-running mode or with finite repetition rate differences while providing a sub-attosecond resolution, which was not feasible with any other approach before.