Spectrally resolved far-fields of terahertz quantum cascade lasers

TL;DR

This paper introduces a rapid method combining a microbolometer array and FTIR spectroscopy to measure spectrally resolved far-fields of multimode terahertz quantum cascade lasers, aiding in understanding their emission properties for sensing applications.

Contribution

A novel, efficient technique for measuring spectrally resolved far-fields of multimode terahertz lasers, validated by simulations and applicable to complex laser cavities.

Findings

Distinguished far-fields of different laser modes

Validated measurements with 3D finite-element simulations

Analyzed mode contributions in multimode random lasers

Abstract

We demonstrate a convenient and fast method to measure the spectrally resolved far-fields of multimode terahertz quantum cascade lasers by combining a microbolometer focal plane array with an FTIR spectrometer. Far-fields of fundamental TM0 and higher lateral order TM1 modes of multimode Fabry-P\'erot type lasers have been distinguished, which very well fit to the results obtained by a 3D finite-element simulation. Furthermore, multimode random laser cavities have been investigated, analyzing the contribution of each single laser mode to the total far-field. The presented method is thus an important tool to gain in-depth knowledge of the emission properties of multimode laser cavities at terahertz frequencies, which become increasingly important for future sensing applications.