Our recent work demonstrated highly efficient coupling of broadband thermal photon radiation between the termination resistors of a superconducting microstrip transmission line measured using a transition edge sensor (TES). A simple modification of this scheme is presented that permits rapid thermometry of micron-scale objects at temperatures below 3 K. Broadband photon noise gives a limiting temperature sensitivity of 3.8 μK for a 1 s integration time for measurements at 0.5 K. In practice, phonon noise in the thermal link between the TES and the heat bath limits the achievable temperature resolution to about 30 μK for a typical TES with noise equivalent power of 2×10−17 W/Hz with the same integration time.
Our recent work demonstrated highly efficient coupling of broadband thermal photon radiation between the termination resistors of a superconducting microstrip transmission line measured using a transition edge sensor (TES). A simple modification of this scheme is presented that permits rapid thermometry of micron-scale objects at temperatures below 3 K. Broadband photon noise gives a limiting temperature sensitivity of 3.8 μK for a 1 s integration time for measurements at 0.5 K. In practice, phonon noise in the thermal link between the TES and the heat bath limits the achievable temperature resolution to about 30 μK for a typical TES with noise equivalent power of 2×10−17 W/Hz with the same integration time.
Transition edge sensors (TESs) are used extensively in millimeter-wave and submillimeter-wave astronomy. The next technological push is to reduce the noise equivalent powers from 10−17 to 10−20 W Hz−1/2 in order to take full advantage of the exceptionally low backgrounds associated with cooled-aperture space telescopes. We describe a lab-on-a-chip (LoC) for measuring the small-signal and noise properties of ultralow-noise microstrip-coupled TESs. The LoC comprises two suspended SiNx membranes, one of which supports a single-mode, variable-temperature blackbody source, and the other a microstrip-coupled TES. The two devices are connected by a superconducting microstrip transmission line. The temperature of the source is determined by Johnson noise thermometry using superconducting quantum interference device readout. In this paper, we describe the theory, layout, operation, and calibration of the experimental system and report on two prototype devices. The LoC concept has many advantages, and already we have been able to assess the optical efficiencies of our TESs. We have started to gain an appreciation of the losses associated with 100–300 GHz microminiature superconducting microstrip transmission lines at low temperatures. The next phase of our work is to apply the technique to ultralow-noise detectors, to study fluctuation phenomena in multimode devices, and to investigate the behavior of more complicated integrated circuits.
Abstract In this paper, we report on the design, fabrication, and characterization of a 220 GHz superconducting transition edge sensor (TES) array developed for ground-based cosmic microwave background (CMB) experiments. Unlike conventional TES arrays adopting thermometers made of bilayer superconducting films, the TES array has thermometers made of simpler single-layer titanium (Ti) film deposited on a suspended silicon nitride (SiN x ) membrane. The thermal weak link is realized by releasing the TES’s thermal island including the Ti thermometer by dry etching with xenon difluoride (XeF2), giving a typical thermal conductance of 25 pW K−1. Its thermal-conductance mechanism is further studied by fitting the measured TES’s complex impedance with a three-block thermal model. The dark and optical noise equivalent power (NEP) of a superconducting TES are both measured. Despite existing lens reflection and dielectric loss in the superconducting microstrip line, its typical optical NEP reaches 100 aW Hz−0.5, which meets the sensitivity requirement for ground-based CMB experiments.
A transition edge sensor (TES) is one of superconducting photon detectors, which has a photon number resolving ability in light pulses. The TES device is a kind of calorimeters operated at an extremely low temperature, and the energy of the photons is measured as a resistance change in a superconducting transition region of the TES. The advantages of the TESs are an excellent energy resolution and a high quantum efficiency. However a response speed is limited due to slow thermal recovery time. To overcome this, we fabricated new TES devices which are based on a titanium superconductor. The critical temperature of our titanium films is around 410 mK, which greatly improves the thermal recovery time. The observed decay time constant of response signals to the light pulses is around several hundreds of ns, that make it possible to operate the devices at a counting rate over 1 MHz. The photon number resolving power is 0.35 eV(FWHM) for a 5 μm size device even at the high operating temperature. The system quantum efficiency is 65 % by embedding the TES films in an optical structure with a high reflection dielectric mirror and an anti-reflection coatings fabricated by an ion beam assisted sputtering method. These features are very promising for high speed photon number resolving applications in the quantum information field.
To improve both scalability and noise-filtering capability of a transition-edge sensor (TES), a new concept of a thin-film detector is suggested, which is based on embedding a microbridge TES into a high-Q planar GHz-range resonator weakly coupled to a 50-Ω-readout transmission line. Such a TES element is designed as a hot-electron microbolometer coupled to a THz-range antenna and as a load of the resonator at the same time. A weak THz signal coupled to the antenna heats the microbridge TES, thus reducing the quality factor of the resonator and leading to a power increment in the readout line. The power-to-power conversion gain, an essential figure of merit, is estimated to be above 10. To demonstrate the basic concept, we fabricated and tested a few submicrometer-sized devices from Nb thin films for operation temperature about 5 K. The dc and RF characterization of the new device is made at a resonator frequency about 5.8 GHz. A low-noise high-electron mobility transistor amplifier is used in our TES experiments without the need for a SQUID readout. The optical sensitivity to blackbody radiation within the frequency band 600-700 GHz ismeasured as (2.7 ± 0.9) × 10-14W/√Hz at Tc≈ 5 K at bath temperature ≈1.5 K.
In order to improve the performance of photon-number-resolving (PNR) superconducting transition-edge sensor (TES) devices, it is advantageous to use device materials with excellent thermal properties. We present TES devices based on a titanium/silver (Ti/Ag) bi-layer structure which is expected to enable high-performance devices due to the high thermal conductivity and low specific heat of silver. We describe the fabrication process for our Ti/Ag devices and report their characterization results. We use the fabricated devices with critical temperature of about 190 milli-Kelvin for PNR experiments at 1550 nm and shorter wave lengths, and demonstrate high energy resolution of 0.17 eV and fast thermal recovery time of about 700 ns at the bias point of the best energy resolution. Judicious characterization of the device performance under various working conditions verifies its reliability and robustness and proves that the Ti/Ag TES can support high-performance PNR measurement in demanding quantum optics experiments.
Transition-edge sensors (TESs) are among the most promising technologies for single-photon detection, offering high quantum efficiency, low dark count rates, and energy-resolving capabilities. However, optimal TES performance typically requires ultra-low temperatures below 100 mK, necessitating bulky dilution refrigerators or adiabatic demagnetization refrigerators, which limits their practical deployment. In this work, we demonstrate a titanium-based TES optimized for 1064 nm photon detection that achieves high performance at an elevated bath temperature of 220 mK—approximately 90% of its superconducting transition temperature, making it compatible with more compact sorption refrigerators. Through the integration of an optical cavity, a detailed complex impedance and noise characterization, and a systematic investigation of dark count sources, the detector achieves a system detection efficiency exceeding 97%, an energy resolution of 240 meV, and an intrinsic dark count rate as low as 2 × 10−4 cps. These findings significantly expand the applicability of TES single-photon detectors to practical photon-counting systems, such as quantum information and infrared astronomy.