Lasing versus lasing without inversion in an optically thin gain medium near a metal surface

TL;DR

This paper develops a first-principles theory for lasing in an optically thin active layer near a metal surface, revealing how medium thickness influences lasing with or without inversion, with numerical results for erbium-doped glass.

Contribution

It introduces a rigorous model accounting for local fields near a reflective surface, showing the transition between conventional lasing and lasing without inversion based on medium thickness.

Findings

Gain medium thickness controls lasing conditions.

Lasing without inversion is achievable near a metal surface.

Numerical simulations demonstrate telecom wavelength lasing in erbium-doped glass.

Abstract

A theory of lasing in an optically thin layer of active centers disposed at a metal surface is developed from first principles. The approach is based on a rigorous account of the local field in a close vicinity of a reflective surface which provides a feedback for dipole oscillations in active centers. It is demonstrated that the gain medium thickness plays a crucial role in the lasing condition and controls a switching from conventional lasing to lasing without inversion. The numerical calculations are carried out for erbium doped glass bordering a gold surface where radiation at telecom wavelength (1532 nm) can be generated.