Carrier density driven lasing dynamics in ZnO nanowires

TL;DR

This paper investigates the ultrafast lasing dynamics in high-quality ZnO nanowires, revealing how electron-hole plasma formation and carrier density influence emission onset, wavelength shifts, and refractive index changes across a wide temperature range.

Contribution

It introduces a comprehensive model linking carrier density, refractive index changes, and lasing dynamics in ZnO nanowires, supported by experimental time-resolved photoluminescence data.

Findings

Lasing onset time can be below 5 ps in the lasing regime.

Red shift of lasing modes is explained by carrier density effects.

The model accurately predicts refractive index evolution post-excitation.

Abstract

We report on the temporal lasing dynamics of high quality ZnO nanowires using time-resolved micro-photoluminescence technique. The temperature dependence of the lasing characteristics and of the corresponding decay constants demonstrate the formation of an electron-hole plasma to be the underlying gain mechanism in the considered temperature range from 10 K to 300 K. We found that the temperature dependent emission onset-time ($t_{\text{on}}$) strongly depends on the excitation power and becomes smallest in the lasing regime, with values below 5 ps. Furthermore, the observed red shift of the dominating lasing modes in time is qualitatively discussed in terms of the carrier density induced change of the refractive index dispersion after the excitation laser pulse. This theory is supported by extending an existing model for the calculation of the carrier density dependent complex refractive index for different temperatures. This model coincides with the experimental observations and reliably describes the evolution of the refractive index after the excitation laser pulse.