Optical sensor including a Bragg grating structure for enhanced sensitivity
AssigneeGEC-Marconi Limited
InventorsRosemary Cush, William J. Stewart
Life of this patent
Estimating the term…
Abstract
This invention describes a technique for improving the sensitivity of a resonant mirror sensor which has particular applications in areas involving sensing at an interface such as immunosensing using immobilized antibodies. By the introduction of a Bragg grating structure in the sensor, there is produced enhanced dispersion and hence enhanced sensitivity in the region close to the band edge. This improves the detection limit of the sensor without changing the composition or involving the sensor size and allows more sensitive operation at reduced incident angles.
Claims4
An optical sensor comprising a dielectric resonant cavity including a dielectric resonant layer bounded at its opposite plane faces by a sensing layer and a coupling layer;
- a substrate layer supporting said coupling layer and a Bragg grating provided in any one of said layers to enhance the sensitivity of the optical sensor, the period of the grating, .DELTA., being selected so that a forbidden band is formed for a range of wavevectors, centered on the wavevector, K, which satisfies the condition K..DELTA.=m.pi.(m is an integer), such that the resonant wavevector of the sensor is outside the forbidden band, in a range adjacent the edge of the forbidden band, the size of the forbidden band being dependent upon amplitude of the grating variation.
Dependencies are inferred from the claim text.