Terahertz Quantum Cascade Laser Local Oscillator

NASA and NASA funded missions/instruments such as Aura (EOS CH-1)/MLS (Microwave Limb Sounder), SOFIA/GREAT and STO 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 compact, frequency agile, phase/frequency locked, power stabilized, single mode quantum cascade laser (QCL) system with > 2mW power output. The system includes distributed feedback grating (DFB) QCL arrays packed with multiple devices on a single semiconductor die with individual devices lasing at different frequencies. The source will be frequency agile over 150 GHz with center frequencies ranging from 2 to 5 THz range. The DFB QCL array will be packaged in a high-reliability Stirling cycle cooler. The source will be phase/frequency locked to a stable microwave reference synthesizer which allows continuous phase-locking ability over the THz laser tunable range with 2 THz, with reduction of LO linewidth, and absolute frequency accuracy and with output power stabilized to reduce system noise. The whole system will be in a compact package which can be further reduced for a flight instrument.

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 DFB QCL array LO would be a frequency agile, compact replacement for any gas-laser LO. The resulting source will be compact, reliable, table-top sized THz high power with stabilized frequency and power. 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 of the 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 4) — 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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