Phase-coherent asynchronous optical sampling system

TL;DR

This paper presents a phase-coherent asynchronous optical sampling system with ultra-low residual phase jitter and a phase-coherence time exceeding 8 seconds, achieved through phase-locking femtosecond lasers to a shared cavity-stabilized laser.

Contribution

The study introduces a novel optical sampling system with significantly improved phase coherence and stability, surpassing previous limitations by achieving low residual phase jitter and extended coherence time.

Findings

Residual phase jitter of 0.04 rad at 1 Hz to 5 MHz

Phase-coherence time of at least 10 seconds

Hardware-limited phase coherence time of ~8.15 seconds

Abstract

Mutual phase coherence is the most crucial factor in asynchronous optical sampling system, and its enhancement is commonly achieved by phase-locking both femtosecond lasers to a shared narrow-linewidth cavity-stabilized laser. Here we report such a system with a low residual optical phase jitter at a level of 0.04 rad in a Fourier frequency band from 1 Hz to 5 MHz around 1.55 {\mu}m, corresponding to a timing jitter of 30 as. The residual phase jitter reaches 1 rad at a Fourier frequency between 0.06 Hz and 0.1 Hz, from which the phase-coherence time is inferred at least 10 s. The multi-heterodyne beats experimentally reveal a hardware-limited phase coherence time of ~8.15 s throughout the direct lasing spectral band.