# Defect Line Terahertz Quantum Cascade Laser

## TL;DR

This paper introduces a novel terahertz quantum cascade laser design utilizing a defect mode in a photonic crystal, achieving single mode emission, lower threshold currents, and enhanced mode selectivity for integrated terahertz applications.

## Contribution

The study demonstrates a new defect line design in photonic crystal quantum cascade lasers that improves mode selectivity and reduces lasing threshold, advancing terahertz laser technology.

## Key findings

- Single mode emission achieved
- Lower threshold current compared to standard lasers
- Enhanced mode selectivity in defect line design

## Abstract

We present terahertz quantum cascade lasers operating at a defect mode of a photonic crystal bandgap. This class of devices exhibits single mode emission and low threshold current compared to standard metal-metal lasers. The mode selectivity is an intrinsic property of the chosen fabrication design. The lower lasing threshold effect, already reported in photonic crystal quantum cascade lasers, is further enhanced in the ultra-flat-dispersion defect line. The presented results pave the way for integrated circuitry operating in the terahertz regime and have important applications in the field of quantum cascade lasers, spectroscopy and microcavity lasers.