Extremely Narrow, Sharp-Peaked Resonances at the Edge of the Continuum

TL;DR

This paper investigates the phenomenon of extremely narrow and sharp-peaked resonances occurring at the edge of the continuum in driven potential wells and dielectric thin films, with analytical, numerical, and experimental validation, highlighting potential applications in optical filtering.

Contribution

It introduces and analyzes the critical narrowing and shape change of resonances at the continuum edge, combining semi-analytical, numerical, and experimental approaches.

Findings

Resonances become extremely narrow and sharp at the continuum boundary.

The phenomenon is validated experimentally with light reflection measurements.

Potential application in narrow-band optical filtering.

Abstract

We report a critical narrowing of resonances of a driven potential well, when their eigenfrequencies approach the edge of the continuum. The resonances also obtain unusual sharp-peak shapes at the continuum boundary. The situation can be realized for the electromagnetic wave propagating across the dielectric thin films with a periodically modulated interface(s). We show the general phenomenon semi-analytically on a simplified model of a driven quantum potential well, also by rigorous numerical analysis of Maxwell equations for the wave propagation across the thin film with a modulated interface(s). We justify the phenomenon experimentally, by the measurements of light reflection from the dielectric thin film deposited on a periodically modulated surface. The narrow and sharp-peak resonances can be used for an efficient narrow-band frequency- and spatial filtering of light.