Energy resolution of aluminium photon-counting MKID detectors at visible and near-infrared wavelengths

22 Jul 2019, 15:10
15m
Auditorium G. Testori (Milano)

Auditorium G. Testori

Milano

Piazza Città di Lombardia, 1, 20124 Milano MI
Oral Presentation Low Temperature Detector Development and Physics Orals LM 001

Speaker

Pieter de Visser (SRON)

Description

To answer the question whether there is life on exoplanets a new generation of instruments is required that will take spectra of these planets. Future instruments for visible/near-IR wavelengths therefore require noiseless, photon counting detectors, with energy resolution.
Microwave Kinetic Inductance Detectors (MKIDs) are photon-counting superconducting detectors which provide energy resolution in each pixel. The resolving power (R=E/dE) of MKIDs is theoretically limited to R~100 by Fano statistics, depending on the material. Current detectors reach R~10, thus we need to better understand the physics and improve the detector limits.
We present an energy resolution study with aluminium MKIDs, which we have previously shown to understand very well and which are the most sensitive terahertz MKIDs to date. We deliberately study a well-understood material first, before moving to higher resistivity materials, which are favourable from a photon-absorption standpoint. We have measured the resolving power of Al MKIDs, which from their THz sensitivity promise R~60 at 400 nm. We operate the MKIDs at 120 mK and illuminate them with 4 lasers between 402-1550 nm. Firstly, we find that our BK7 and fused silica windows are open to low frequency stray light (< 1 THz), which limits the measured energy resolution. After mounting the optical fiber at 100mK, we show that we reach a resolving power of 17 at 402 nm to 10 at 1550 nm from the histogram of single-photon events, with a large (factor ~4) discrepancy between the signal-to-noise and the histogram resolution. We expect that the loss of hot phonons, while down converting the photon energy to quasiparticles, is already showing up at this energy-resolution level. Al MKIDs are particularly sensitive to phonon losses because of the long pair-breaking time. We will present experiments to study the effectiveness of phonon trapping measures.

Student (Ph.D., M.Sc. or B.Sc.) N
Less than 5 years of experience since completion of Ph.D N

Primary authors

Pieter de Visser (SRON) Mr Vignesh Murugesan (SRON, Netherlands Institute for Space Research) David Thoen (Delft University of Technology) Prof. Jochem Baselmans (SRON)

Presentation Materials