# 18th International Workshop on Low Temperature Detectors (LTD-18)

Jul 22 – 26, 2019
Milano
Europe/Rome timezone

## Complex impedance of optical transition-edge sensors with sub-microsecond response

Jul 23, 2019, 5:45 PM
1h 15m
Piazza Città di Lombardia (Milano)

### Piazza Città di Lombardia

#### Milano

Piazza Città di Lombardia, 1, 20124 Milano MI
Poster Detector readout, signal processing, and related technologies

### Speaker

Dr Kaori Hattori (AIST)

### Description

Optical transition edge sensor (TES) detectors which can resolve an energy of a single optical photon have proven desirable in quantum information and biological imaging. Optical TESs were designed to have a high detection efficiency at a specific wavelength and has achieved nearly 100 % at the wavelength. They have been proven to have the sensitivity at a wide bandwidth from near-infrared to visible regions. The energy resolution was typically 0.1 to 0.2 eV. Higher energy resolution is required for an application of the TESs in multicolor fluorescence microscopy. A question arising here is if we have reached the theoretical limit of the energy resolution. To calculate the limit, we need to measure parameters such as the temperature sensitivity $\alpha$ and the current sensitivity $\beta$, extracted from the complex impedance.
The optical TES is characterized by: (1) its small size (typically 5 to 10 $\mu$m) to be sensitive to the low-energy photons and (2) a fast response time (< 1 $\mu$s) determined by the heat capacity and weak thermal coupling between electrons and phonons in the detector. To extract $\beta$ of a sub-microsecond TES, the complex impedances need to be measured at high frequencies (> 1 MHz), where the parasitic impedance in the circuit and reflections of electrical signals due to discontinuities in the characteristic impedance of the readout circuits become significant. To reduce the parasitic impedance and the discontinuities, we have replaced legacy twisted cables with coaxial ones and obtained cleaner transfer function of the readout. Figures show the complex impedance of a TES sensitive to MHz-electrical perturbations. We will discuss the theoretical limit of the energy resolution and a possible thermal model of the TES.

Student (Ph.D., M.Sc. or B.Sc.) N N

### Primary author

Dr Kaori Hattori (AIST)

### Co-authors

Mr Ryo Kobayashi (AIST, Nihon Univ.) Ms Sachiko Takasu (AIST) Dr Daiji Fukuda (AIST, Nihon university)