Speaker
Description
The transition edge sensor (TES) is a microcalorimeter that exploits the sharp increase in resistance at the transition between superconducting and normal conducting states. This steep transition characteristic enables even small energy depositions to produce large changes in resistance, resulting in sufficiently large current signal generation. TES technology has been primarily developed for X/gamma-ray detectors used in high-resolution spectroscopy applications. More recently, our research group has focused on developing smaller TES devices aiming for photon-number-resolving measurements in the near-infrared (NIR) wavelength ranges.
The optical TES has a smaller sensitive area to reduce its heat capacity and hence enables high energy resolution. The sensitive area is normally around 10 micrometers square, which is enough for obtaining the lights from single-mode optical fibers.
Our optical TESs are made of thin Iridium films, which have transition temperatures of around 300 mK. The fabricated devices are cooled down by adiabatic demagnetization refrigerator (ADR) or dilution refrigerator (DR) to around 100 mK. The Joule-heating from a TES and the cooling by the refrigerator are balanced and hence the TES is stabilized at its transition temperature. TES devices are irradiated by pulsed laser sources at the room temperature through the optical fibers which are wired inside the refrigerators. Our TES showed the energy resolution of around 0.4 eV and successfully showed photon number resolving capabilities in NIR wavelength regions. We are currently working on devices with fast timing capabilities aiming for wide applications.
