8-beam local oscillator array at 47 THz generated by a phase grating and a quantum cascade laser
We present an 8-beam local oscillator (LO) for the astronomically significant [OI] line at 4.7 THz. The beams are generated using a quantum cascade laser (QCL) in combination with a Fourier phase grating. The grating is fully characterized using a third order distributed feedback (DFB) QCL with a single mode emission at 4.7 THz as the input. The measured diffraction efficiency of 74.3% is in an excellent agreement with the calculated result of 75.4% using a 3D simulation. We show that the power distribution among the diffracted beams is uniform enough for pumping an array receiver. To validate the grating bandwidth, we apply a far-infrared (FIR) gas laser emission at 5.3 THz as the input and find a very similar performance in terms of efficiency, power distribution, and spatial configuration of the diffracted beams. Both results represent the highest operating frequencies of THz phase gratings reported in the literature. By injecting one of the eight diffracted 4.7 THz beams into a superconducting hot electron bolometer (HEB) mixer, we find that the coupled power, taking the optical loss into account, is in consistency with the QCL power value.
- Research Organization:
- Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)
- Sponsoring Organization:
- USDOE National Nuclear Security Administration (NNSA); USDOE Office of Science (SC)
- Grant/Contract Number:
- NA0003525; AC04-94AL85000
- OSTI ID:
- 1408782
- Alternate ID(s):
- OSTI ID: 1411612
- Report Number(s):
- SAND-2017-8886J; OPEXFF
- Journal Information:
- Optics Express, Journal Name: Optics Express Vol. 25 Journal Issue: 24; ISSN 1094-4087
- Publisher:
- Optical Society of America (OSA)Copyright Statement
- Country of Publication:
- United States
- Language:
- English
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