NASA and NASA funded missions/instruments such as Aura/MLS (Microwave Limb Sounder), SOFIA/upGREAT 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 multi-element heterodyne receiver.
LongWave Photonics is proposing to develop a high power, phase/frequency-locked, single mode, THz QC-VECSEL quantum cascade
laser (QC-VECSEL) system with >2 mW cw power (estimated 5mW) at 77K at 3.4 THz and deliver it to NASA at the end of Phase II. QC-VECSELs operating at 4.7 THz band will also be investigated and will be delivered to NASA if the performance is suitable. The system includes a THz QC-VECSEL gain chip based on metasurface gain structure with an integrated cavity adjustment structure. The VECSEL LO will be packaged in a high-reliability Stirling cycle cooler with modification to minimize vibration noise. The source could be frequency locked to a stable microwave reference with <100 kHz line width. Moreover, the unique tuning mechanism for QC-VECSEL could achieve 250 GHz of tuning at 4.7 THz, meeting the design requirement for future HERO instrument on Origins Space Telescope (OST).
NASA applications include the use of the QCL as an LO for >2 THz receivers for future missions. Here the narrow linewidth (<100 kHz) of the QC-VECSEL can be used to resolve Doppler-limited low-pressure gasses (~MHz linewidth). The QC-VECSEL LO will be a compact replacement for any gas-laser LO. The resulting source will be a compact, reliable, table-top, frequency stabilized, yet highly tunable, high power THz LO with high beam quality which can sufficiently pump multi-element HEB receiver array.
Initial applications are research markets for low-pressure gas spectroscopy. The narrow line width and the ability to provide real-time frequency information of THz radiation also has great appeal. THz QC-VECSEL can also provide fast frequency sweeping ability which opens new applications such as THz optical tomography (OCT).