We design, fabricate, and measure a novel spectrometer based on meta-surface structures, aiming to optimize its spectroscopic resolution within a band from 1.7 to 2.5 THz. The latter corresponds to a bandwidth of 38%, being comparable with a grating spectrometer. The meta-surfaces apply unit cells that consist of double-anchor structures based on gold, polyimide and gold triple layers. Several quantum cascade lasers that operate at slightly different frequencies around 2.1 THz were used to validate the spectrometer. We have measured a resolving power R of 273 and an efficiency of 78 %. Our results demonstrate for the first time a centimeter-sized, light weight FIR spectrometer with a promising resolution, which has potential to replace the half meter-sized, heavy grating based spectrometers in this wavelength band.
We have demonstrated three 4×2 hot electron bolometer (HEB) mixer arrays for operation at local oscillator (LO) frequencies of 1.4, 1.9 and 4.7 THz, respectively. These arrays consist of spiral antenna coupled NbN HEB mixers combined with elliptical lenses. These are to date the highest pixel count arrays using a quasi-optical coupling scheme at supra-THz frequencies. At 1.4 THz, we obtained an average double sideband mixer noise temperature of 330 K, a mixer conversion loss of 5.2 dB, and an optimum LO power of 210 nW. The array at 1.9 THz has an average mixer noise temperature of 425K, a mixer conversion loss of 6.4 dB, and an optimum LO power of 190 nW. For the array at 4.7 THz we obtained an average mixer noise temperature of 715 K, a mixer conversion loss of 8.9 dB, and an optimum LO power of 240 nW. We found the arrays to be uniform regarding the mixer noise temperature with a standard deviation of 3-4%, the conversion loss with a standard deviation of 8-11%, and optimum LO power with a standard deviation of 5-6%. The noise bandwidth was also measured, being 3.5 GHz for the three arrays. These performances are comparable to previously reported values in the literature for single pixels and also other detector arrays at similar frequencies. Our arrays met the requirements and were employed in the Galactic/Extra-Galactic ULDB Spectroscopic Terahertz Observatory (GUSTO), a NASA balloon borne observatory. GUSTO launched from Antarctica on the 31st December 2023 having a successful flight of 57 days, the longest ever recorded by NASA for such mission profile.
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