CompleteSmatrix in a microwave cavity at room temperature

Abstract

We experimentally study the widths of resonances in a two-dimensional microwave cavity at room temperature. By developing a model for the coupling antennas, we are able to discriminate their contribution from those of ohmic losses to the broadening of resonances. Concerning ohmic losses, we experimentally put to evidence two mechanisms: damping along propagation and absorption at the contour, the latter being responsible for variations of widths from mode to mode due to its dependence on the spatial distribution of the field at the contour. A theory, based on an S-matrix formalism, is given for these variations. It is successfully validated through measurements of several hundreds of resonances in a rectangular cavity.

Direct Observation of Localized Modes in an Open Disordered Microwave Cavity

“…Moreover, the observed spectral widths Γ leak due to leaking at the boundary, are also in fair agreement with the gross evaluation given by Γ leak exp(−2R/ξ loc ) with R the distance from the center of the mode to the boundary [24]. More specifically, when reducing the scattering region, hence reducing R, we were able to ascertain the above relationship by extracting values of Γ leak from the total experimental widths thanks to a proper evaluation of the contribution of ohmic losses to the latter [13]. All this confirms that the exponentially vanishing field of such modes at the boundary involves all the scatterers of the system through complex multiple interference effects.…”

“…By using an appropriate fitting procedure [20] we extracted the spectral widths of the resonances. Only a few widths take values close to those expected taking only the ohmic losses into account [13], whereas the vast majority are significantly larger. These purely ohmic widths could be associated to resonances which very likely do not reach the absorbing foam at the boundary.…”

Correlation Functions of Impedance and Scattering Matrix Elements in Chaotic Absorbing Cavities

“…plete S-matrix [9] in microwave cavities, properties of resonance widths [10] in such systems at room temperatures, dissipation of ultrasonic energy in elastodynamic billiards [11], fluctuations in microwave networks [12] (see also references in these papers). Theoretically, statistics of reflection, delay times and related quantities were considered first in the strong [13] or weak [14] absorption limits at perfect coupling, and very recently at arbitrary absorption and coupling [15][16][17][18][19].…”

Inhomogeneous losses and complexness of wave functions in chaotic cavities

“…Most of the works concerns the case of uniform absorption which is responsible for homogeneous broadening Γ hom of all the modes (resonance states). However, in some experimentally relevant situations like, e.g., complex reverberant structures [4,5] or even microwave cavities at room temperature [6,7] one should take into account also localizedin-space losses which lead to an inhomogeneous part Γ inh of the widths which varies from mode to mode. As a result, the neighboring modes experience nontrivial correlations due to interference via one and the same decaying / dissipative environment that result in the complex-valued wave functions of corresponding resonance states.…”