Tuning the Quantum Efficiency of Random Lasers - Intrinsic Stokes-Shift and Gain

TL;DR

This paper presents a theoretical analysis of how Stokes-shift and non-radiative processes affect the quantum efficiency of solid state random lasers, revealing limitations in mode confinement explanations.

Contribution

It couples Vollhardt-Woelfle theory with lasing dynamics to analyze the impact of non-linearity and Stokes-shift on random laser efficiency and mode behavior.

Findings

Stokes-shift reduces quantum efficiency due to non-radiative losses.

Near threshold, the spot size decreases significantly, indicating increased losses.

Stokes-shifts alone do not fully explain mode confinement regimes.

Abstract

We report the theoretical analysis for tuning the quantum efficiency of solid state random lasers. Vollhardt-Woelfle theory of photonic transport in disordered non-conserving and open random media, is coupled to lasing dynamics and solved positionally dependent. The interplay of non-linearity and homogeneous non-radiative frequency conversion by means of a Stokes-shift leads to a reduction of the quantum efficiency of the random laser. At the threshold a strong decrease of the spot-size in the stationary state is found due to the increase of non-radiative losses. The coherently emitted photon number per unit of modal surface is also strongly reduced. This result allows for the conclusion that Stokes-shifts are not sufficient to explain confined and extended mode regimes.