Advancements in Degenerate Distributed Feedback Lasing

TL;DR

This paper demonstrates a novel degenerate distributed feedback laser operating near a degenerate band edge, achieving low-threshold, single-frequency lasing in a compact, mirrorless cavity with potential applications in communications, sensing, and spectroscopy.

Contribution

It introduces a degenerate distributed feedback laser near a degenerate band edge with exceptional scaling properties, enabling minimal footprint, single-frequency lasing without mirrors.

Findings

Large quality factor scales with the fifth power of cavity length.

Lasing threshold scales inversely with the fifth power of the number of unit cells.

Potential for compact, efficient single-frequency lasers.

Abstract

We advance the concept of degenerate distributed feedback (DDFB) lasing in a double grating photonic structure that operates near a degenerate band edge (DBE) to achieve a robust single-frequency lasing regime. The DBE is an exceptional point of degeneracy (EPD) of fourth order involving four coalescing Bloch eigenmodes. A DDFB photonic cavity operating close to the DBE frequency is shown to display a large quality factor that scales with the fifth power of the cavity length. Upon the inclusion of gain, the DDFB cavity displays a low lasing threshold with the exceptional scaling as the inverse of the fifth power of the double grating length, i.e., ${\alpha}_{D,th} \propto 1/N^5$, where $N$ is the number of waveguide unit cells making the mirrorless cavity. The work proposed here shows a path to single-frequency lasing mode using a mirrorless cavity with minimal device footprint. The DDFB laser is very attractive for various applications including communications, sensing, and spectroscopy.