Near perfect mode overlap between independently seeded, gain-switched lasers

TL;DR

This paper presents a pulsed light seeding technique that significantly enhances mode overlap between independent gain-switched lasers, achieving near-perfect interference and high Hong-Ou-Mandel visibility for quantum information uses.

Contribution

The authors introduce a pulsed light seeding method that synchronizes frequency chirp and reduces jitter, enabling near-perfect mode overlap between independent lasers.

Findings

Near perfect mode overlap demonstrated

Hong-Ou-Mandel dip visibility of 0.499 achieved

Monte-Carlo simulations match experimental results

Abstract

We drastically improve the mode overlap between independently seeded, gain-switched laser diodes operating at gigahertz repetition rates by implementing a pulsed light seeding technique. Injecting pulsed light reduces the emission time jitter and enables frequency chirp synchronization while maintaining random optical phases of the emitted laser pulses. We measure interference of these pulsed sources both in the macroscopic regime, where we demonstrate near perfect mode overlap, and in the single photon regime, where we achieve a Hong-Ou-Mandel dip visibility of 0.499+/-0.004, thus saturating the theoretical limit of 0.5. The measurement results are reproduced by Monte-Carlo simulations with no free parameters. Our light source is an ideal solution for generation of high rate, indistinguishable coherent pulses for quantum information applications.