Patent ID: 6218194
Filing Date: 2001-04-17
Classification: G01N,Y10S

Abstract:
A method for monitoring the interaction of a first molecular species in a sample with a second molecular species, said method comprising:providing a sensor device comprising a substrate having a waveguide formed on at least part of the surface thereof, the waveguide having a first major surface which constitutes an interface between the waveguide and the substrate and a second major surface upon which the second molecular species is immobilized, wherein one or both of at least a region of the first major surface and at least a region of the second major surface is formed with a refractive index modulation having a single period, and where both first and second major surfaces are formed with such a refractive index modulation, the periods of both of said refractive index modulations being the same;contacting a sample containing the first molecular species with the second major surface so that interaction between the first molecular species and the second molecular species can take place;irradiating said refractive index modulation with an incident beam of monochromatic incident light having a wavelength and the incident beam having a radius,varying an angle of incidence of said light or the wavelength of said light through a range of angles or wavelengths respectively, said range including an angle or a wavelength, as the case may be, at which a guided mode is excited in said waveguide;monitoring intensity of light reflected from said refractive index modulation as a function of the angle of incidence or wavelength of the incident light; anddetermining that angle of incidence or wavelength at which light reflected from the refractive index modulation has a maximum intensity, such that at that angle of incidence or wavelength at which light reflected from the refractive index modulation has a maximum intensity there is destructive interference of transmitted components of incident light, and the radius of the incident beam at the refractive index modulation exceeds a coupling length of the guided mode in the waveguide, and wherein that angle of incidence or wavelength at which light reflected from the refractive index modulation has a maximum intensity is dependent upon interaction of the first molecular species with the second molecular species.