Transition from non-resonant to resonant random lasers by the geometrical confinement of disorder

TL;DR

This paper demonstrates how geometrical confinement in random lasers causes a transition from non-resonant to resonant lasing behavior, with experimental evidence showing different emission thresholds based on device geometry.

Contribution

The study introduces a controlled transition between non-resonant and resonant random laser regimes through device geometry manipulation.

Findings

Larger volumes exhibit non-resonant behavior with decreasing thresholds.

Confined geometries act as cavities, inducing resonant laser behavior.

A phase diagram of the transition is experimentally established.

Abstract

We report on a novel kind of transition in random lasers induced by the geometrical confinement of the emitting material. Different dye doped paper devices with controlled geometry are fabricated by soft-lithography and show two distinguished behaviors in the stimulated emission: in the absence of boundary constraints the energy threshold decreases for larger laser volumes showing the typical trend of diffusive {\it non-resonant} random lasers, while when the same material in lithographed into channels, the walls act as cavity and the {\it resonant} behavior typical of standard lasers is observed. The experimental results are consistent with the general theories of random and standard lasers and a clear phase diagram of the transition is reported.