Far-field characterization of the thermal dynamics in lasing microspheres

TL;DR

This paper investigates the thermal dynamics of lasing microspheres on a substrate, revealing how their thermal behavior scales with size and is dominated by heat transfer to the substrate, supported by experiments and simulations.

Contribution

It provides a detailed characterization of the thermal behavior of lasing microspheres and introduces a simplified model for heat conduction at the microscale.

Findings

Thermal lifetimes are about 2 ms and scale with microsphere radius.

Thermal dynamics are independent of pump power within studied range.

Finite-Element simulations match experimental results, highlighting substrate heat dissipation.

Abstract

This work reports the dynamical thermal behavior of lasing microspheres placed on a dielectric substrate while they are homogeneously heated-up by the top-pump laser used to excite the active medium. The lasing modes are collected in the far-field and their temporal spectral traces show characteristic lifetimes of about 2 ms. The latter values scale with the microsphere radius and are independent of the pump power in the studied range. Finite-Element Method simulations reproduce the experimental results, revealing that the thermal dynamics is dominated by the heat dissipated towards the substrate through the medium surrounding the contact point. The characteristic system scale regarding thermal transport is of few hundreds of nanometers, thus enabling an effective toy model for investigating heat conduction in non-continuum gaseous media and near-field radiative energy transfer.