4×2 HEB receiver at 4.7 THz for GUSTO

Abstract

We have demonstrated three 4×2 hot electron bolometer (HEB) mixer arrays for operation at local oscillator (LO) frequencies of 1.46, 1.9 and 4.7 THz, respectively. They 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 measured an average double sideband mixer noise temperature of 330 K, a mixer conversion loss of 5.7 dB, and an optimum LO power of 210 nW. The array at 1.9 THz has an average mixer noise temperature of 420K, a conversion loss of 6.9 dB, and an optimum LO power of 190 nW. For the array at 4.7 THz, we obtained an average mixer noise temperature of 700 K, a conversion loss of 9.7 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 7-10%, 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. Our arrays meet the requirements of the Galactic/Extra-Galactic ULDB Spectroscopic Terahertz Observatory (GUSTO), a NASA balloon borne observatory, and are therefore scheduled to fly as part of the payload, which is expected to be launched in December 2023.

Optical design of the Orbiting Astronomical Satellite for Investigating Stellar Systems

“…The sensitivity required to detect and spectrally resolve these lines is provided by a large aperture coupled with state-of-the-art heterodyne receivers. 10 The terahertz heterodyne receivers need to be periodically (∼20 s) chopped on and off-targets. This translates to a minimum required FoV of 0.01 deg (6 arcmin).…”

Parametric design study of the Orbiting Astronomical Satellite for Investigating Stellar Systems (OASIS) space telescope

“…OASIS targets far-infrared (far-IR) transitions of water and its isotopologues, as well as HD and other molecular species, from 0.45 to 4.7 THz (660 to 63 μm) that are obscured by the Earth's atmosphere. The sensitivity required to detect and spectrally resolve these lines is provided by a large aperture coupled with state-of-the-art heterodyne receivers 10 . The terahertz heterodyne receivers need to be periodically (~20 s) chopped on and off targets.…”

High Accuracy Pointing for Quasi-Optical THz Mixer Arrays

“…Because the sensitivity of current HEB mixers is approaching the quantum noise limit [9] there is a need to develop multi-pixel array receivers in order to improve mapping speeds of future instruments. Recent important technology improvements, such as high power QCLs [10], [11] and LO multiplexing schemes based on a Fourier phase grating [12], offer solutions to fulfill the existing demands for multipixel THz heterodyne systems for airborne [13], balloon borne [14], [15] and possibly future space [16] THz observatories.…”

“…GUSTO is a NASA ultra-long duration balloon borne terahertz observatory [15] that will employ three focal-plane arrays based on quasi-optical HEB mixers to simultaneously measure the fine structure lines of [NII], [CII] and [OI] at 1.4, 1.9 and 4.7 THz, respectively. It requires the use of compact focal-plane arrays, each of which consists of 8 pixels in a 4×2 configuration.…”