Whispering gallery mode resonator based ultra-narrow linewidth external cavity semiconductor laser

TL;DR

This paper presents a miniature external cavity semiconductor laser with ultra-narrow linewidth achieved through whispering gallery mode resonator feedback, demonstrating significant linewidth reduction and high frequency stability.

Contribution

The work introduces a self-injection locked DFB laser with a high-Q whispering gallery mode resonator, achieving unprecedented linewidth narrowing and stability improvements.

Findings

Linewidth reduction factor >10,000

Instantaneous linewidth <200 Hz

Allan deviation as low as 3x10^(-12) at 20 us

Abstract

We demonstrate a miniature self-injection locked DFB laser using resonant optical feedback from a high-Q crystalline whispering gallery mode resonator. The linewidth reduction factor is greater than 10,000, with resultant instantaneous linewidth less than 200 Hz. The minimal value of the Allan deviation for the laser frequency stability is 3x10^(-12) at the integration time of 20 us. The laser possesses excellent spectral purity and good long term stability.