arXiv subjects

Miha Furlan

Publications and source records attributed to Miha Furlan.

6 recordsLinked to original sources

arXiv2006

Imaging of single infrared, optical, and ultraviolet photons using distributed tunnel junction readout on superconducting absorbers

Single-photon imaging spectrometers of high quantum efficiency in the infrared to ultraviolet wavelength range, with good timing resolution and with a vanishing dark count rate are on top of the wish list in earth-bound astronomy, material and medical sciences, or quantum information technologies. We review and present improved operation of a cryogenic detector system potentially offering all these qualities. It is based on a superconducting absorber strip read out with superconducting tunnel junctions. The detector performance is discussed in terms of responsivity, noise properties, energy and position resolution. Dynamic processes involved in the signal creation and detection are investigated for a basic understanding of the physics, and for possible application-specific modifications of device characteristics.

physics.ins-det↗

arXiv2006

Cryogenic small-signal conversion with relaxation oscillations in Josephson junctions

Broadband detection of small electronic signals from cryogenic devices, with the option of simple implementation for multiplexing, is often a highly desired, although non-trivial task. We investigate and demonstrate a small-signal analog-to-frequency conversion system based on relaxation oscillations in a single Josephson junction. Operation and stability conditions are derived, with special emphasis on noise analysis, showing the dominant noise sources to originate from fluctuation processes in the junction. At optimum conditions the circuit is found to deliver excellent noise performance over a broad dynamic range. Our simple models apply within the regime of classical Josephson junction and circuit dynamics, which we confirm by experimental results. A discussion on possible applications includes a measurement of the response to a cryogenic radiation detector.

physics.ins-det↗

arXiv2005

Self-cooling cryogenic microcalorimeters made of SINIS junctions

High quality low leakage SINIS devices made of Al-AlMn-Al layers were fabricated for energy dispersive single photon detection. Information on different heat flow channels was extracted from the measured dynamics of detector signals due to X-ray events. At the optimum operation point, the extracted effective electron temperature decreased from 88 mK down to 43 mK due to self-cooling, roughly doubling the detector sensitivity.

physics.ins-det↗

arXiv2005

New frequency-modulation readout based on relaxation oscillations

Scaling of multi-pixel cryogenic detectors for imaging becomes increasingly difficult with size due to complexity of readout circuitry and cryogenic constraints (thermal load from wiring). We propose and demonstrate a new readout scheme based on a highly stable RF oscillator composed of a superconducting tunnel junction which exhibits relaxation oscillations. The oscillation frequency is almost linear with the analog bias signal over a wide operation range. The frequency signals from different detectors can be combined into one single readout line. The current noise of an optimized circuit is about 5 pA/sqrt(Hz), which is comparable to standard SQUID amplifiers. We show experimental data from `stand-alone' operation as well as response to microcalorimeter X-ray signals.

physics.ins-det↗

arXiv2002

Electrometry on charge traps with a single-electron transistor

Background charge fluctuators are studied individually by means of a modified single-electron pump. Operation of the device in a feedback mode allows electrometric sensing of the charged background and its behavior upon electric potential variations due to geometrically different gates. Pulse height spectra and hysteresis of charge trapping transitions are discussed as a specific signature of distinct fluctuators. The location of individual traps is determined from the experimental data and based on electrostatic calculations.

cond-mat.mes-hall↗

arXiv2000

Modelling background charge rearrangements near single-electron transistors as a Poisson process

Background charge rearrangements in metallic single-electron transistors are modelled in two-level tunnelling systems as a Poisson process with a scale parameter as only variable. The model explains the recent observation of asymmetric Coulomb blockade peak spacing distributions in metallic single-electron transistors. From the scale parameter we estimate the average size of the tunnelling systems, their density of states, and the height of their energy barrier. We conclude that the observed background charge rearrangements predominantly take place in the substrate of the single-electron transistor.

cond-mat.mes-hall↗