Patent ID: 7537734

Claim:
An apparatus for performing a specific binding assay, the apparatus comprising: a composite waveguide comprising: a substrate comprising a first optical material of refractive index n 1 and having a first planar surface and an opposite second surface, and a waveguide film comprising a second optical material having a refractive index n 2 which is greater than refractive index n 1 , said waveguide film disposed on said first planar surface of said substrate; capture molecules, associated with said waveguide film, for interacting selectively with at least one type of selected analyte molecule; a light source operably disposed to direct a light beam into said composite waveguide for propagation by total internal reflection therein; a light detection device positioned to collect light emitted from a surface of said waveguide film; and an optical coupling element comprised of a waveguide coupler disposed on an upper surface of said waveguide film and opposite said first planar surface of said substrate, wherein said waveguide coupler is further comprised of an input waveguide that is comprised of an optical material having a refractive index n 3 and a thickness of between about 0.5 mm and about 5 mm and a precise spacing layer to evanescently couple light into said waveguide film across said precise spacing layer, said spacing layer comprises an optical material having a refractive index n 4 , where n 4 <n 2 and n 4 <n 3 .