Gain dynamics in a heterogeneous terahertz quantum cascade laser

TL;DR

This study measures the gain recovery time in a heterogenous terahertz quantum cascade laser, revealing how pump strength and temperature influence the dynamics, with implications for laser performance optimization.

Contribution

It provides the first detailed measurement of gain recovery times in a heterogenous terahertz quantum cascade laser using terahertz pump-probe spectroscopy.

Findings

Gain recovery time ranges from 34 to 50 ps.

Stronger pumping shortens the recovery time.

Higher temperature slows down gain recovery.

Abstract

The gain recovery time of a heterogeneous active region terahertz quantum cascade laser is studied by terahertz-pump,i terahertz-probe spectroscopy. The investigated active region, which is based on a bound-to-continuum optical transition with an optical phonon assisted extraction, exhibits a gain recovery time in the range of 34$\,$-$\,$50$\,$ps dependent on the operation condition of the laser. The recovery time gets shorter for stronger pumping of the laser while the recovery dynamics slows down with increasing operation temperature. These results indicate the important role of the intracavity light intensity for the fast gain recovery.