Performance of Hybrid NbTiN-Al Microwave Kinetic Inductance Detectors as Direct Detectors for Sub-millimeter Astronomy

TL;DR

This paper demonstrates the second-generation hybrid NbTiN-Al microwave kinetic inductance detectors (MKIDs) that are photon noise limited, highly responsive, and capable of reading out thousands of pixels simultaneously for sub-millimeter astronomy applications.

Contribution

The paper introduces the second-generation hybrid NbTiN-Al MKIDs with improved responsivity and scalability, enabling large arrays for sub-mm imaging and spectroscopy.

Findings

Photon noise limited in phase and amplitude readout for loading levels ≥10 fW

Simultaneous readout of approximately 8000 pixels

Operates within 0.09 to 1.1 THz frequency range

Abstract

In the next decades millimeter and sub-mm astronomy requires large format imaging arrays and broad-band spectrometers to complement the high spatial and spectral resolution of the Atacama Large Millimeter/sub-millimeter Array. The desired sensors for these instruments should have a background limited sensitivity and a high optical efficiency and enable arrays thousands of pixels in size. Hybrid microwave kinetic inductance detectors consisting of NbTiN and Al have shown to satisfy these requirements. We present the second generation hybrid NbTiN-Al MKIDs, which are photon noise limited in both phase and amplitude readout for loading levels $P_{850GHz} \geq 10$ fW. Thanks to the increased responsivity, the photon noise level achieved in phase allows us to simultaneously read out approximately 8000 pixels using state-of-the-art electronics. In addition, the choice of superconducting materials and the use of a Si lens in combination with a planar antenna gives these resonators the flexibility to operate within the frequency range $0.09 < \nu < 1.1$ THz. Given these specifications, hybrid NbTiN-Al MKIDs will enable astronomically usable kilopixel arrays for sub-mm imaging and moderate resolution spectroscopy.