Reflection and Scattering of Electromagnetic Waves in Spatial Grids Consisting of Multiple Lossy Waveguides

Abstract

Medical diagnosis technologies using X-ray and optical wave transmitted tomogra- phy have been rapidly developed with computer processing. X-ray and optical transmitted fleld characteristics in CT, that depend on biomedical absorption due to bio-molecules and atoms, yield biomedical information of human body tissues and cells. However, X-ray and optical trans- mitted fleld signals at receiving output of diagnosis CT sensors are disturbed by scattering waves in random bio-medical inhomogeneities around objects of body tissues and cells. Before sig- nal processing by computer, hardware tools of spatial flltering of disturbing scattering flelds for absorption characteristics in bio-medical tissues and cells are very useful system functions. Spatial flltering of scattered flelds by grid arrays consisting of transversely multiple lossy waveg- uides is one of excellent device function for spatial flltering in X-ray and optical diagnosis. Spa- tial fllter of grid arrays consisting of multiple lossy waveguides is waveguide array consisting of waveguides with transparent cores and lossy clads. Each waveguide has core size, clad size and waveguide length. Scattered flelds in random bio-medical media are incident on input plane of spatial fllter array, and coupled to lower modes of low losses for small scattering angles and higher modes of large losses for large scattering angles, in lossy waveguide array. Low angle scattered flelds couple to lower modes and large angle scattered flelds couple to lossy higher modes. Scattered flelds coupled to lossy higher modes are flltered in lossy grid arrays. Mode characteris- tics in lossy grid arrays excited by scattered fleld in random bio-medical media are discussed by mode expansion methods using boundary condition at input plane of lossy grid array, and flltered flelds at output plane of lossy grid array are shown by integral equations using Green's dyadics. Mode characteristics and flltered flelds are also investigated by the Wiener-Hopf method with spectral functions.