Giant negative group time delay by microwave adaptors

¹ Anhalt University of Applied Sciences - Bernburger Str. 55, 06366 Köthen, Germany, EU
² Agilent Technologies - Campus Kronberg 7, 61476 Kronberg, Germany, EU
³ Physics Department, University of Cologne - Zülpicher Str. 77, 50937 Köln, Germany, EU

^a g.nimtz@uni-koeln.de

Received: 31 May 2012
Accepted: 5 June 2012

Abstract

A Fabry-Perot–like interferometer with two microwaveguide adaptors as reflectors creates a passive dielectric medium with a negative group delay time due to polarization shift. In that case rectangular with circular waveguides are adapted. A rotational strain of the polarization vector by one of the adaptors is coupled with the excitation of a drastic negative group velocity. The adapted rectangular and circular waveguides have the same dispersion. The input rectangular waveguide mode is linearly polarized, whereas the basic mode of the adapted circular waveguide is circularly polarized. A 20 m long circular waveguide connects the input with the output adaptor. Experiments are reproduced in the frequency and in the time domain. A polarization turn of the two different handed reflected circular wave modes causes the observed negative group velocity.