An optical phase-locking with large and tunable frequency difference based on vertical-cavity surface-emitting laser

TL;DR

This paper introduces a new method for phase-locking two lasers with a large, tunable frequency difference using VCSELs, enabling precise control and applications like atomic resonance experiments.

Contribution

A novel technique for phase-locking two lasers with a tunable frequency difference up to 35 GHz using VCSEL sidebands and injection seeding.

Findings

Achieved phase locking with a frequency difference up to 35 GHz.

Sideband suppression rate exceeds 30 dB at 30 μW seed power.

Heterodyne linewidth between lasers is less than 1 Hz.

Abstract

We present a novel technique to phase-lock two lasers with controllable frequency difference. In our setup, one sideband of a current modulated Vertical-Cavity Surface-Emitting Laser (VCSEL) is phase locked to the master laser by injection seeding, while another sideband of the VCSEL is used to phase lock the slave laser. The slave laser is therefore locked in phase with the master laser, with a frequency difference tunable up to about 35 GHz. The sideband suppression rate of the slave laser is more than 30dB at 30 uW seed power. The heterodyne spectrum between master and slave has a linewidth of less than 1 Hz. A coherent population trapping resonance of rubidium is achieved using such beams.