Optical Spectral Singularities as Threshold Resonances

TL;DR

This paper demonstrates that spectral singularities in optical systems occur at threshold gain conditions and proposes a method to create a tunable laser operating precisely at this threshold, linking mathematical features to physical laser behavior.

Contribution

It establishes a connection between spectral singularities and threshold resonances in optical systems, providing a practical approach to design threshold-based tunable lasers.

Findings

Spectral singularities occur at the gain threshold in optical systems.

A method to construct tunable lasers operating at threshold gain is proposed.

The study applies to semiconductor gain media and threshold laser design.

Abstract

Spectral singularities are among generic mathematical features of complex scattering potentials. Physically they correspond to scattering states that behave like zero-width resonances. For a simple optical system, we show that a spectral singularity appears whenever the gain coefficient coincides with its threshold value and other parameters of the system are selected properly. We explore a concrete realization of spectral singularities for a typical semiconductor gain medium and propose a method of constructing a tunable laser that operates at threshold gain.