No Arabic abstract
We have measured a response to a black body radiation and noise of the cold-electron bolometers. The experimental results have been fitted by theoretical model with two heat-balance equations. The measured noise has been decomposed into several terms with the help of theory. It is demonstrated that the photon noise exceeds any other noise components, that allows us to conclude that the bolometers see the photon noise. Moreover, a peculiar shape of the noise dependence on the absorbed power originates completely from the photonic component according to the theory. In the additional experiment on heating of the cryostat plate together with the sample holder we have observed nearly independence of the noise on the electron temperature of the absorber, which has provided another proof of the presence of the photon noise in the first experiment.
We demonstrate photon noise limited performance in both phase and amplitude readout in microwave kinetic inductance detectors (MKIDs) consisting of NbTiN and Al, down to 100 fW of optical power. We simulate the far field beam pattern of the lens-antenna system used to couple radiation into the MKID and derive an aperture efficiency of 75%. This is close to the theoretical maximum of 80% for a single-moded detector. The beam patterns are verified by a detailed analysis of the optical coupling within our measurement setup.
Superconducting nanowire single photon detectors are capable of single-photon detection across a large spectral range, with near unity detection efficiency, picosecond timing jitter, and sub-10 $mu$m position resolution at rates as high as 10$^{9}$ counts/s. In an effort to bring this technology into nuclear physics experiments, we fabricate Niobium Nitride nanowire detectors using ion beam assisted sputtering and test their performance in strong magnetic fields. We demonstrate that these devices are capable of detection of 400 nm wavelength photons with saturated internal quantum efficiency at temperatures of 3 K and in magnetic fields potentially up to 5 T at high rates and with nearly zero dark counts.
We describe optical characterisation of a Strained Silicon Cold Electron Bolometer (CEB), operating on a $350~mathrm{mK}$ stage, designed for absorption of millimetre-wave radiation. The silicon Cold Electron Bolometer utilises Schottky contacts between a superconductor and an n++ doped silicon island to detect changes in the temperature of the charge carriers in the silicon, due to variations in absorbed radiation. By using strained silicon as the absorber, we decrease the electron-phonon coupling in the device and increase the responsivity to incoming power. The strained silicon absorber is coupled to a planar aluminium twin-slot antenna designed to couple to $160~mathrm{GHz}$ and that serves as the superconducting contacts. From the measured optical responsivity and spectral response, we calculate a maximum optical efficiency of $50~%$ for radiation coupled into the device by the planar antenna and an overall noise equivalent power (NEP), referred to absorbed optical power, of $1.1 times 10^{-16}~mathrm{mbox{W Hz}^{-1/2}}$ when the detector is observing a $300~mathrm{K}$ source through a $4~mathrm{K}$ throughput limiting aperture. Even though this optical system is not optimised we measure a system noise equivalent temperature difference (NETD) of $6~mathrm{mbox{mK Hz}^{-1/2}}$. We measure the noise of the device using a cross-correlation of time stream data measured simultaneously with two junction field-effect transistor (JFET) amplifiers, with a base correlated noise level of $300~mathrm{mbox{pV Hz}^{-1/2}}$ and find that the total noise is consistent with a combination of photon noise, current shot noise and electron-phonon thermal noise.
We perform experimental and theoretical study of the parallel-series arrays of Cold-Electron Bolometers (CEBs) integrated into a cross-slot antenna and composed with an immersion silicon lens. The purpose is to determine the absorption efficiency, the responsivity and the noise equivalent power (NEP) of the bolometers. The absorbed power has been found in two independent ways. The comparison of two approaches gives better understanding of the system and secures from misinterpretations. The first approach is fitting of the bolometer IV curves with solutions of heat-balance equations. The second approach is modeling of electromagnetic properties of the system, including an antenna, lens, optical can, band-pass filters and black body source. The difference between both methods does not exceed $30%$. The optimization of experimental setup is proposed to approach the photon limited detection mode.
The origin and the evolution of the universe are concealed in the evanescent diffuse extragalactic background radiation (DEBRA). To reveal these signals, the development of innovative ultra-sensitive bolometers operating in the gigahertz band is required. Here, we review the design and experimental realization of two bias-current-tunable sensors based on one dimensional fully superconducting Josephson junctions: the nanoscale transition edge sensor (nano-TES) and the Josephson escape sensor (JES). In particular, we cover the theoretical basis of the sensors operation, the device fabrication, their experimental electronic and thermal characterization, and the deduced detection performance. Indeed, the nano-TES promises a state-of-the-art noise equivalent power (NEP) of about $5 times 10^{-20}$ W$/sqrt{text{Hz}}$, while the JES is expected to show an unprecedented NEP of the order of $10^{-25}$ W$/sqrt{text{Hz}}$. Therefore, the nano-TES and JES are strong candidates to push radio astronomy to the next level.