A horn-coupled millimetre-wave on-chip spectrometer based on lumped-element kinetic inductance detectors
Abstract
Context. Millimetre-wave astronomy is an important tool for both general astrophysics studies and cosmology. A large number of unidentified sources are being detected by the large field-of-view continuum instruments operating on large telescopes.
Aims: New smart focal planes are needed to bridge the gap between the large bandwidth continuum instruments operating on single-dish telescopes and high spectral and angular resolution interferometers (e.g. ALMA in Chile and NOEMA in France). The aim is to perform low to medium spectral resolution observations and select a lower number of potentially interesting sources (i.e. high-redshift galaxies) for further follow-up.
Methods: We have designed, fabricated, and tested an innovative on-chip spectrometer sensitive in the 85-110 GHz range. It contains 16 channels, each of which covers a frequency band of about 0.2 GHz. A conical horn antenna coupled to a slot in the ground plane collects the radiation and guides it to a millimetre-wave microstrip transmission line placed on the other side of the mono-crystalline substrate. The millimetre-wave line is coupled to a filter-bank spectrometer. Each filter is capacitively coupled to a lumped-element kinetic inductance detector (LEKID). The microstrip configuration provides the benefit of low loss, due to the mono-crystalline substrate, and protects the LEKIDs from illumination by stray un-filtered light.
Results: The prototype spectrometer exhibits a spectral resolution R = λ/Δλ ≈ 300. The optical noise equivalent power is in the low 10−16 W Hz−1/2 range for an incoming power of about 0.2 pW per channel. The device is polarisation-sensitive, with a cross-polarisation lower than 1% for the best channels.
- Publication:
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Astronomy and Astrophysics
- Pub Date:
- April 2023
- DOI:
- 10.1051/0004-6361/202244887
- arXiv:
- arXiv:2209.02484
- Bibcode:
- 2023A&A...672A...7C
- Keywords:
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- instrumentation: detectors;
- instrumentation: spectrographs;
- Astrophysics - Instrumentation and Methods for Astrophysics;
- Physics - Instrumentation and Detectors
- E-Print:
- Submitted to Astronomy &