Diffraction anomaly sensor having grating coated with protective dielectric layer

A sensor for assaying a plurality of substances in a sample comprising:

• a substrate having a plurality of parallel grooves in a surface;
• a metal layer formed outwardly from the surface of the substrate, the metal layer substantially conforming to the grooved surface of the substrate;
• and
• a plurality of substantially non-overlapping dielectric layers formed along the metal layer for suppressing reflectance of an incident light beam having a polarization component parallel to the grooves of the substrate.

A method for assaying a substance in a sample comprising the steps of:

• providing a sensor having a metal diffraction grating coated with a dielectric layer;
• emitting a light beam having a polarization component parallel to grooves in the metal diffraction grating;
• exposing the sensor with the light beam over a plurality of incident angles;
• detecting a first diffraction anomaly angle during the first exposing step at which zero-order reflectance of the incident light changes;
• interacting the sensor with the sample;
• exposing the sensor a second time with a light beam over the plurality of incident angles;
• detecting a second diffraction anomaly angle during the second exposing step;
• and
• determining a measure of the substance in the sample as a function of the first angle and the second angle.

A method for assaying a substance in a sample comprising the steps of:

• providing a sensor having a metal diffraction grating having a plurality of grooves, wherein the metal diffraction is coated with a dielectric layer;
• exposing the sensor with a light beam having a component parallel to the grooves of the grating, and further wherein the component propagates substantially within the dielectric layer when the sensor is exposed with the light beam at a diffraction anomaly angle;
• interacting the sensor with the sample;
• and
• determining a measure of the substance in the sample as a function of a shift in the diffraction anomaly angle.

A method for assaying a plurality of substances in a sample comprising the steps of:

• providing a sensor having a metal diffraction grating coated with a plurality of substantially non-overlapping dielectric layers, each dielectric layer for interacting with at least one of the substances in the sample, wherein the diffraction grating has a plurality of parallel grooves;
• selectively exposing at least one of the dielectric layers with a light beam at a corresponding diffraction anomaly angle such that a component of the light beam having a polarization parallel to the grooves in the sensor propagates substantially within the exposed dielectric layer;
• interacting the sensor with the sample;
• and
• determining a measure for each substance in the sample as a function of a shift in the diffraction anomaly angle of the corresponding dielectric layer capable of interacting with the substance.

A system for assaying a substance in a sample, comprising:

• a sensor sensitized for interacting with the substance in the sample comprising:
• a substrate having a grooved surface,
• a metal layer formed outwardly from the surface of the substrate, the metal layer substantially conforming to the grooved surface of the substrate, and
• a dielectric layer formed outwardly from the metal layer;
• a light source exposing the sensor with a light beam at an angle of incidence;
• a detector receiving light reflected from the sensor, the detector responsive to light polarized parallel to the grooves in the surface of the substrate;
• and
• a controller coupled to the detector for calculating a measure of the substance in the sample as a function of an anomaly angle at which a change in zero-order reflectance of the light beam.