Multi-line lasing in the broadly tunable ammonia quantum cascade laser pumped molecular laser

TL;DR

This paper demonstrates a broadly tunable ammonia-based quantum cascade laser pumped molecular laser capable of multi-line terahertz lasing, achieving unprecedented tunability and power levels through experimental validation.

Contribution

It introduces a novel ammonia QPML with extensive tunability and multi-line lasing capabilities, expanding the potential for terahertz applications.

Findings

Tunable from 0.762 to over 4.5 THz

Achieved up to 0.33 mW power from a compact cavity

Demonstrated simultaneous and cascaded multi-line lasing

Abstract

Gaseous ammonia has previously been demonstrated as a compelling gain medium for a quantum cascade laser pumped molecular laser (QPML), exhibiting good power efficiency but limited tunability. Here we explore the potential of the ammonia QPML to produce powerful, broadly tunable terahertz frequency lasing on rotational and pure inversion transitions. After theoretically predicting possible laser frequencies, pump thresholds, and efficiencies, we experimentally demonstrate unprecedented tunability -- from 0.762 to more than 4.5 THz -- by pumping Q- and R-branch infrared transitions with widely tunable quantum cascade lasers. We additionally demonstrate two types of multi-line lasing: simultaneous pure inversion and rotation-inversion transitions from the same pumped rotational state, and cascaded lasing involving transitions below the pumped rotational state. We report single frequency power levels as great as 0.33 mW from a low volume laser cavity.