Maximizing performance of quantum cascade laser-pumped molecular lasers

TL;DR

This paper models and analyzes how to optimize the performance of QCL-pumped molecular lasers, revealing key dependencies on pressure and cavity design to maximize terahertz output power.

Contribution

It introduces a validated three-level model to explore the effects of physical parameters on laser performance, guiding optimal cavity and pressure conditions for high power output.

Findings

Maximum power occurs near pump saturation minimization.

Pressure has a greater impact on performance than cavity dimensions.

Over 10 mW of tunable terahertz power can be achieved with optimized design.

Abstract

Quantum cascade laser (QCL)-pumped molecular lasers (QPMLs) have recently been introduced as a new source of powerful (>1 mW), tunable (>1 THz), narrow-band (<10 kHz), continuous-wave terahertz radiation. The performance of these lasers depends critically on molecular collision physics, pump saturation, and on the design of the laser cavity. Using a validated three-level model that captures the essential collision and saturation behaviors of the QPML gas nitrous oxide (N2O),we explore how threshold pump power and output terahertz power depend on pump power, gas pressure, as well as on the diameter, length, and output-coupler transmissivity of a cylindrical cavity.The analysis indicates that maximum power occurs as pump saturation is minimized in a manner that depends much more sensitively on pressure than on cell diameter, length, or transmissivity. A near-optimal compact laser cavity can produce more than 10 mW of power tunable over frequencies above 1 THz when pumped by a multi-watt QCL.