Abstract-Wideband on-chip terahertz spectrometer based on a superconducting filterbank

Akira Endo, Kenichi Karatsu, Alejandro Pascual Laguna, Behnam Mirzaei, Robert Huiting, David J. Thoen, Vignesh Murugesan, Stephen J. C. Yates, Juan Bueno, Nuri van Marrewijk, Sjoerd Bosma, Ozan Yurduseven, Nuria Llombart, Junya Suzuki, Masato Naruse, Pieter J. de Visser, Paul P. van der Werf, Teun M. Klapwijk, Jochem J. A. Baselmans

https://arxiv.org/abs/1901.06934

Terahertz spectrometers with a wide instantaneous frequency coverage for passive remote sensing are enormously attractive for many terahertz applications, such as astronomy, atmospheric science and security. Here we demonstrate a wide-band terahertz spectrometer based on a single superconducting chip. The chip consists of an antenna coupled to a transmission line filterbank, with a microwave kinetic inductance detector behind each filter. Using frequency division multiplexing, all detectors are read-out simultaneously creating a wide-band spectrometer with an instantaneous bandwidth of 45 GHz centered around 350 GHz. The spectrometer has a spectral resolution of F/ΔF=380 and reaches photon-noise limited sensitivity. We discuss the chip design and fabrication, as well as the system integration and testing. We confirm full system operation by the detection of an emission line spectrum of methanol gas. The proposed concept allows for spectroscopic radiation detection over large bandwidths and resolutions up to F/ΔF∼1000, all using a chip area of a few cm2. This will allow the construction of medium resolution imaging spectrometers with unprecedented speed and sensitivity.

Abstract-Surface wave control for large arrays of microwave kinetic inductance detectors

Stephen J. C. Yates, Andrey M. Baryshev, Ozan Yurduseven, Juan Bueno, Kristina K. Davis, Lorenza Ferrari, Willem Jellema, Nuria Llombart, Vignesh Murugesan, David J. Thoen, Jochem J. A. Baselmans

(Submitted on 7 Jul 2017)

https://arxiv.org/abs/1707.02142

Large ultra-sensitive detector arrays are needed for present and future observatories for far infra-red, submillimeter wave (THz), and millimeter wave astronomy. With increasing array size, it is increasingly important to control stray radiation inside the detector chips themselves, the surface wave. We demonstrate this effect with focal plane arrays of 880 lens-antenna coupled Microwave Kinetic Inductance Detectors (MKIDs). Presented here are near field measurements of the MKID optical response versus the position on the array of a reimaged optical source. We demonstrate that the optical response of a detector in these arrays saturates off-pixel at the ∼−30 dB level compared to the peak pixel response. The result is that the power detected from a point source at the pixel position is almost identical to the stray response integrated over the chip area. With such a contribution, it would be impossible to measure extended sources, while the point source sensitivity is degraded due to an increase of the stray loading. However, we show that by incorporating an on-chip stray light absorber, the surface wave contribution is reduced by a factor >10. With the on-chip stray light absorber the point source response is close to simulations down to the ∼−35 dB level, the simulation based on an ideal Gaussian illumination of the optics. In addition, as a crosscheck we show that the extended source response of a single pixel in the array with the absorbing grid is in agreement with the integral of the point source measurements.