Superconducting quantum detectors

Abstract:

We consider the cut-off frequencies of high-order modes in boxed submillimetre-wave microstrip filters. It is shown that many of the filters in use at the present time are not cut off in the way that the designers imagine. It is also shown that for ease of manufacture the height of the microstrip channel should be 0.7 times the width and the thickness of the quartz substrate should be 0.5 times the width. This optimum geometry suggests that the upper frequency limit of conventional waveguide components is 1THz. © 1993 Plenum Publishing Corporation.

Abstract:

The oscillation polarization ellipse in a molecular beam disc resonator maser is shown to be strongly rotated when a weak axial magnetic field is applied. The phenomenon is a microwave analogue of a similar behaviour observed in gas lasers, and is interpreted here in terms of lumped resonator anisotropies. © 1985.

Abstract:

A rectangular flat-roof and plane mirror combination type of microwave open resonator, with a mirror spacing of a single half-wavelength ( lambda =12.5 mm), is investigated experimentally in the context of molecular beam masers. The flat-roof resonator possesses the property of a radiation field that is extensive in the direction of the mirror crease, but concentrated in the transverse direction by an amount dictated by the roof-top pitch, down to a value of about a wavelength. The associated reduction of diffraction loss leads to an increase of Q value of almost twice that of a flat mirror resonator of similar dimensions. Resonances are easy to find and are insensitive to rotations of the roof edge about the plane mirror. The resonator is tunable over several GHz. A lifting of the frequency degeneracy of mode polarisation is reported. the application of the flat-roof resonator is illustrated by results obtained by its incorporation into a high-resolution molecular beam maser spectrometer and oscillator. It could also find an application in pulsed molecular beam Fourier transform spectroscopy.