Tunable, High-Power Terahertz Quantum Cascade Laser Local Oscillator

NASA and NASA funded missions/instruments such as Aura/MLS (Microwave Limb Sounder), SOFIA/GREAT and STO/STO-2 have demonstrated the need for local oscillator (LO) sources between 30 and 300 um (1 and 10 THz). For observations >2 THz, technologically mature microwave sources typically have microwatt power levels which are insufficient to act as LOs for a heterodyne receivers. LongWave Photonics is proposing to develop a high power, frequency tunable, phase/frequency-locked, single mode, External Cavity THz quantum cascade laser (ECT-QCL) system with >2 mW average power output and a clear path to increase the power to >10 mW. The system includes a THz QC gain chip based on SISP or metal-meal waveguide with integrated horn or lens structure to reduce facet reflectivity. Frequency selective external feedback will be frequency tunable over 100's of GHz, with center frequencies ranging from 2 to 5 THz. The gain chip will be packaged in a high-reliability Stirling cycle cooler. The source will be phase/frequency locked to a stable microwave reference synthesizer with <100 kHz line width.

NASA applications include the use of the QCL as an LO for >2 THz receivers for future missions. Here the narrow line width (<100 kHz) of the QCLs can be used to resolve Doppler-limited low pressure gasses (~MHz linewidth). The exterval cavity QCL LO will be a frequency tunable, compact replacement for any gas-laser LO. The resulting source will be a compact, reliable, table-top sized THz high power with stabilized frequency. It will be an easy-to-use platform for NASA researchers to study the performance of other key components in the receiver such as Schottky or HEB mixers.

Initial applications for this technology are mainly research markets for low pressure gas spectroscopy. The narrow line width and the ability to provide real-time frequency information and freqeuncy tunability of THz radiation also has great appeal. Another potential application is to replace THz gas laser used for THz detector power calibration. Long-term applications include industrial uses for trace gas detection. For industrial applications, the use of high-reliability, compact Stirling cycle coolers would greatly increase the usability of these QCL devices, which have traditionally required liquid nitrogen cooling or larger cryocooling systems.

This is early/mid-stage (TRL 3) — the most realistic path in is NASA SBIR/STTR, which funds small businesses and research institutions to develop technology aligned with NASA's needs (equity-free, phased funding). Check whether a current SBIR/STTR solicitation topic overlaps with this project's technology area, or contact the project directly (above) to ask.

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