Superconducting quantum detectors

Abstract:

We report the successful operation of a 700 GHz SIS finline mixer employing a Nb tunnel junction and Nb transmission lines. In particular, we discuss the properties of a new mixer feed and the influence of-tuning on the mixer performance. Experimental and simulation work shows that the performance of the mixer below the superconducting gap is strongly dependent on the electrical properties of the tuning stub, while at frequencies above the gap the mixer performance is dominated by both tuning and transmission lines losses.

Abstract:

We describe a procedure for modelling the optical behaviour of planar, bolometric imaging arrays. Arrays of this kind axe being developed for the next generation of ground-based and space-borne, submillimetre-wave and far-infrared, astronomical telescopes. A unique feature of the scheme is that the partially coherent vector fields associated with the individual pixels are traced through the optical system simultaneously. Simultaneous tracing is achieved by propagating the second-order statistical properties of the total field. In the paper, we describe the theoretical basis of our method, and present the results of a number of illustrative simulations.

Abstract:

Microwave transmission through HTSC circular waveguides close to the cutoff conditions has been investigated. Applicative consequences of a sharp decrease in the transmitted power observed in the vicinity of the superconducting transition are discussed. (C) 2002 Elsevier Science B.V. All rights reserved.

Abstract:

Compact quasi-optics are difficult to design with any confidence using techniques developed for visible wavelengths. In this paper we investigate the performance of existing software design tools (ASAP, CODE V, GLAD) as well as a Gaussian beam mode analysis technique not yet available as commercial software. We have devised a set of test cases and used these to study the underlying methodologies and physics of these packages and we probe their suitability for the analysis of submillimetre-wave systems and components. We have used the physical optics package GRASP as our benchmark software.

Abstract:

A procedure is described for calculating the power coupled between partially coherent waveguide fields that are in different states of coherence. The method becomes important when it is necessary to calculate the power transferred from a distributed source S to a distributed load L through a length of multimode metallic, or dielectric, waveguide. It is shown that if the correlations between the transverse components of the electric and magnetic fields of S and L are described by coherence matrices M and M', respectively, then the normalized average power coupled between them is (eta) = Tr[MM']/Tr[M]Tr[M'], where Tr denotes the trace. When the modal impedances are equal, this expression for the coupled power reduces to an equation derived in a previous paper [J. Opt. Soc. Am. A 18, 3061 (2001)], by use of thermodynamic arguments, for the power coupled between partially coherent free-space beams.