Ghassan Yassin

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.

Abstract:

Elliptical oscillation in a molecular beam maser operated with a disc resonator is shown to exhibit a polarization bistability. The various experimental conditions under which the phenomenon arises are discussed and an interpretation given in terms of anisotropic properties of the resonator and the state selected molecular beam. © 1981.

Abstract:

It is shown that observation of elliptical oscillation at frequencies ~ 24 GHz in a molecular beam maser operated with a disk resonator is facilitated by the display of the polarisation ellipse on an oscilloscope. Details of the method together with illustrative results are presented and further applications discussed. © 1981, The Institution of Electrical Engineers. All rights reserved.