Showing papers by "Kaori Hattori published in 2020"

Development of an Optical Transition-Edge Sensor Array

Abstract: Transition-edge sensors (TESs) exhibiting high energy resolution for single optical photons have been applied to photon-counting microscopy for biological imaging. This paper discusses the development of TES arrays with large effective areas to expand the field of view of photon-counting microscopy and has fabricated an optical TES array comprising a Ti/Au bilayer on a Si substrate. Thermal interference due to Joule power did not affect the time constant and energy resolution of a detector in the TES array, even though the Joule power in the detector was changed by 23%. The photon signal crosstalk between adjacent detectors was − 40 dB which was negligible. Heat conduction through the Si substrate was dominant in the photon signal crosstalk between adjacent detectors.

Microwave SQUID Multiplexer for Readout of Optical Transition Edge Sensor Array

Abstract: Photon imaging technology is applied in various research fields such as quantum information communication and biological imaging. We have been developing photon-counting devices using optical transition edge sensors (TES). We demonstrated a single-photon spectroscopic imaging system comprising an optical TES and a scanning microscope. However, a great number of TES pixels are required to increase the field of view in the imaging system. To read out the TES array, output signals need to be multiplexed. Microwave SQUID multiplexer (MW-Mux) is a kind of frequency multiplexing method with a carrier wave having a frequency of several GHz, and it can be used to widen the frequency band. In this paper, we report the first demonstration on readout of an optical TES with MW-Mux.

Complex impedance of a transition-edge sensor with sub-μs time constant

Abstract: Optical transition edge sensor (TES) detectors that can resolve the energy of a single optical photon have proven to be desirable in multicolor fluorescence microscopy. Here, detectors with a higher energy resolution can distinguish dyes having similar or closer emission wavelengths, thus enabling the observation of multiple kinds of dyes simultaneously. To improve energy resolution, it is necessary to know how different the measured energy resolution is from the limit determined by the temperature sensitivity αI and current sensitivity βI, as extracted from the complex impedance. Due to the very fast response of an optical TES (the time constant is shorter than 1 µs), the complex impedance must be measured up to frequencies larger than 10 MHz. However, at high frequencies, the parasitic impedance in the circuit and reflections of electrical signals caused by discontinuities in the characteristic impedance of the readout circuits become significant. To reduce these effects, twisted pair cables are replaced with coaxial ones in this work; thus, a cleaner transfer function of the readout at high frequencies is obtained. The measured impedance of the studied TES is consistent with that given by the single-block model.