Abstract
A noiseless, photon-counting detector, which resolves the energy of each photon, could radically change astronomy, biophysics, and quantum optics. Superconducting detectors promise an intrinsic resolving power at visible wavelengths of due to their low excitation energy. We study superconducting energy-resolving microwave kinetic inductance detectors (MKIDs), which hold particular promise for larger cameras. A visible and near-infrared photon absorbed in the superconductor creates a few thousand quasiparticles through several stages of electron-phonon interaction. Here we demonstrate experimentally that the resolving power of MKIDs at visible to near-infrared wavelengths is limited by the loss of hot phonons during this process. We measure the resolving power of our aluminum-based detector as a function of photon energy using four lasers with wavelengths between –. For detectors on thick / and sapphire substrates the resolving power is limited to – for the respective wavelengths, consistent with the loss of hot phonons. When we suspend the sensitive part of the detector on a 110-nm-thick membrane, the measured resolving power improves to –, respectively. The improvement is equivalent to a factor stronger phonon trapping on the membrane, which is consistent with a geometrical phonon propagation model for these hot phonons. We discuss a route towards the Fano limit by phonon engineering.
1 More- Received 12 March 2021
- Revised 30 March 2021
- Accepted 17 August 2021
DOI:https://doi.org/10.1103/PhysRevApplied.16.034051
© 2021 American Physical Society
Physics Subject Headings (PhySH)
synopsis
Trapped Phonons Improve Photon Detection
Published 30 September 2021
Researchers more than double the frequency resolution of a superconducting single-photon detector through phonon trapping.
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