Diffraction anomaly sensor having grating coated with protective dielectric layer

Abstract

A method and apparatus for optically assaying a targeted substance in a sample using a diffraction anomaly grating sensor. The optical sensor has a diffraction grating coated with at least one dielectric layer such that the sensor is sensitized to interact with the targeted substance. Upon interaction, light incident upon the sensor at a particular angle propagates through the dielectric, thereby exhibiting a dip in zero-order reflectance. Advantages of the present invention include facilitating increased sensitivity while protecting the metal grating from tarnishing and degradation. The present invention also allows for the construction of sensors that are sensitized to a plurality of substances, thus eliminating the need for an operator to reconfigure the sensing system in order to assay different substances.

Description

FIELD OF THE INVENTIONThis invention relates generally to the field of optical sensing and, more particularly, to a method and apparatus for assaying chemical and biological materials.BACKGROUND OF THE INVENTIONRecently, extremely sensitive optical sensors have been constructed by exploiting an effect known as surface plasmon resonance (SPR). These sensors are capable of detecting the presence of a wide variety of materials in concentrations as low as picomoles per liter. SPR sensors have been constructed to detect many biomolecules including dinitrophenyl, keyhole limpet hemocyanin, .alpha.-Feto protein, IgE, IgG, bovine and human serum albumin, glucose, urea, avidin, lectin, DNA, RNA, hapten, HIV antibodies, human transferrin, and chymotrypsinogen. Additionally, SPR sensors have been built which detect chemicals such as polyazulene and various gases including halothane, tricloroethane and carbon tetrachloride.An SPR sensor is constructed by sensitizing a surface of a substrate to ...

AI Technical Summary

Benefits of technology

In yet another embodiment, the invention is a sensor for assaying a plurality of substances in a sample. The sensor includes a substrate having a surface formed in a substantially periodic grooved profile and a metal layer is formed outwardly from the surface of the substrate. A plurality of substantially non-overlapping dielectric layers are formed outwardly from the metal layer. Each of the dielectric layers is capable of suppressing the zero-order reflectance of incident light for at least one corresponding angle of incidence and polarization. This embodiment facilitates the sensing of a plurality of substances in a sample or the reuse of a single sensor for multiple samples having various substances.

Problems solved by technology

Despite these benefits, both current SPR grating sensors and prism-based sensors are susceptible to degradation due to oxidation of the metal film and its continuous exposure to the sample.

Another disadvantage of current SPR sensors is that the metal film causes many biological substances to denature, thus leading to erroneous readings.

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