Optical sensor of bio-molecules using thin-film interferometer

An assembly for use in detecting an analyte in a sample based on thin-film spectral interference, comprising:

• a waveguide;
• a monolithic substrate having a coupling side and a sensing side, wherein the coupling side is optically coupled to the waveguide;
• a thin-film layer directly bonded to the sensing side of the monolithic substrate;
• a coupling medium located between the waveguide and the monolithic substrate and
• the thin film layer comprises a transparent material, a first reflecting surface comprising a layer of analyte binding molecules, and a second reflecting surface between the thin film layer and the monolithic substrate;
• wherein the refractive index of the monolithic substrate is higher than the refractive index of the waveguide, and the refractive index of the coupling medium is in between the refractive indexes of the monolithic substrate and the waveguide;
• wherein the coupling medium has a diameter larger than a diameter of the monolithic substrate;
• wherein the waveguide is configured to transport a light signal from a light source to the sensing side of the monolithic substrate, and the waveguide is further configured to transport light signals from the sensing side of the monolithic substrate to a detector;
• wherein the refractive index of the monolithic substrate is higher than the refractive index of the transparent material of the thin-film layer;
• and
• whereby a spectral interference between light reflected into the waveguide from said first and said second reflecting surfaces varies as analyte molecules in the sample bind to the analyte binding molecules.