Patent ID: 8158398

Claim:
An optical device for providing evanescent radiation, in response to incident radiation, the optical device comprising: a sample chamber having a detection volume for containing a target component in a medium, the detection volume having at least one in-plane dimension smaller than a diffraction limit, the diffraction limit defined by a radiation wavelength of the incident radiation and the medium; aperture defining structures for providing the evanescent radiation, the aperture defining structures having a smallest in plane aperture dimension smaller than the diffraction limit, wherein the detection volume is provided between said aperture defining structures, wherein the aperture defining structures further define a largest in plane aperture dimension, and wherein said largest in plane aperture dimension is larger than said diffraction limit; an optical guiding device for guiding a beam of radiation having a wavelength to have a direction of incidence on the optical device different from an out of plane normal direction for providing the incident radiation incident at the optical device, for providing the evanescent radiation in the detection volume in response to the incident radiation, wherein the optical guiding device is arranged to provide a plane of incidence along both the largest in plane aperture dimension and the out of plane normal direction; and a carrier having a first surface where the aperture defining structures are fixed, the carrier having a second surface opposite the first surface, wherein the guiding device comprises a grating fixed to the second surface.