How resonator design improves performance of quantum cascade laser-pumped molecular lasers

Area of Science:

• Terahertz (THz) technology
• Quantum optics
• Laser physics

Background:

• Widespread terahertz (THz) technology application is hindered by the lack of compact, room-temperature, high-power sources.
• Quantum cascade laser (QCL) pumped molecular lasers (QPMLs) offer tunability and high spectral brightness but face challenges in resonator stability and pump feedback.
• Optimizing THz resonator design is crucial for balancing infrared (IR) absorption and minimizing destabilizing IR feedback.

Purpose of the Study:

• To systematically investigate resonator design strategies for QPMLs.
• To achieve optimal balance between high pump absorption and minimal IR back-reflection in QPMLs.
• To enhance the performance of QPMLs for practical terahertz applications.

Main Methods:

• Experimental comparison of fluoromethane (CH3F) lasing performance in various Fabry-Perot resonator (FPR) geometries.
• Computational modeling of FPR geometries and copper waveguides to evaluate pumping efficiency and back-reflection.
• Correlation of experimental findings with computational modeling results.
• Comparative performance analysis using ammonia (NH3) and carbonyl sulfide (OCS) gain media.

Main Results:

• An optimized FPR design was identified, significantly improving QPML performance.
• Experimental measurements demonstrated a maximum continuous-wave emission power of 2 mW for ammonia (NH3).
• This represents the highest continuous-wave power reported for a QPML to date.
• Computational modeling provided insights into pumping efficiency and back-reflection characteristics for different resonator designs.

Conclusions:

• A clear optimization pathway for designing stable and efficient QPMLs has been established.
• The optimized QPML design shows significant potential for practical terahertz applications.
• Further research can leverage these findings to develop next-generation THz sources.