Chemical detector employing surface plasmon resonance excited using an optical waveguide configured as an asymmetric waveguide coupler
First Claim
1. A surface plasmon sensor apparatus comprising a waveguide, the waveguide having a low refractive index substrate and a high refractive index material deposited on the substrate, a low refractive index buffer layer positioned on the waveguide, a high refractive index tuning layer positioned on the buffer layer, a metallic layer positioned on the tuning layer, a light source for propagating light signals through the waveguide, and a detector for monitoring output signals from the waveguide.
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Abstract
A highly sensitive surface plasmon waveguide sensor monitors the refractive index and thickness of thin adsorbed films. The sensor includes an optical waveguide formed by ion-exchange in a glass substrate, by selective densification of substrate material or by the incorporation of high refractive index materials during deposition of a dielectric layer. Two dielectric thin films are deposited on top of the waveguide. The layer closest to the waveguide has a lower refractive index than the guiding layer to form a buffer layer. The second dielectric layer, or tuning layer, has a higher refractive index. The tuning and buffer layers allow optimization of the resonance wavelength, full-width half maximum of the resonance wavelength range and amplitude of the resonance. The tuning layer is coated with a thin metallic layer, to effect surface plasmon resonance, such as gold, silver, aluminum or one or more semiconducting materials. Alternatively the optical waveguide is coated with the buffer layer and the thin metal layer. The tuning layer and a second buffer layer are deposited on top of the metallic layer. Light is introduced to the waveguide and interaction between the light and the thin metal layer results in attenuation of the TM polarization. The ratio of the TM and TE polarization intensities is monitored by a polarization beam splitter. The relatively unchanged TE polarization intensity serves as an integral reference for the sensor. The sensor has numerous applications in the environmental and biomedical fields.
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28 Claims
- 1. A surface plasmon sensor apparatus comprising a waveguide, the waveguide having a low refractive index substrate and a high refractive index material deposited on the substrate, a low refractive index buffer layer positioned on the waveguide, a high refractive index tuning layer positioned on the buffer layer, a metallic layer positioned on the tuning layer, a light source for propagating light signals through the waveguide, and a detector for monitoring output signals from the waveguide.
- 18. A method for sensing by monitoring refractive indices and thicknesses of adsorbed films comprising the steps of assembling a structure having an optical waveguide, a low refractive index buffer layer on the waveguide, a high refractive index tuning layer on the buffer layer and a metal layer on the tuning layer, adsorbing a film on the metal layer, propagating light through the optical waveguide, detecting a TE polarization intensity and a TM polarization intensity, monitoring a ratio of TE and TM polarization intensities, and evaluating the ratio.
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20. A detection system for detecting agents in an environment in a vicinity of a sensor comprising a light source for generating a light signal, a chopper for interrupting the light signal and for delivering an interrupted light signal, a surface plasmon waveguide sensor, an optical fiber extending between the chopper and the sensor for delivering the interrupted signal from the chopper to the sensor, a polarizer for receiving output signals from the sensor and for emitting polarized signals, and a photodetector for receiving the polarized signals, for monitoring the polarized signals and for determining characteristics of the environment in the vicinity of the sensor.
- 21. A surface plasmon sensor apparatus comprising a waveguide, the waveguide having a low refractive index substrate and a high refractive index layer positioned on top of the substrate, a first low refractive index buffer layer positioned on the waveguide, a metallic layer positioned on the first buffer layer, a high refractive index tuning layer positioned on the metallic layer, a second low refractive index buffer layer positioned on the tuning layer, a light source for propagating light signals through the waveguide, and a detector for monitoring output signals from the waveguide.
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26. A surface plasmon sensor apparatus comprising an array of optical waveguide structures, each waveguide structure further comprising a waveguide having a low refractive index substrate and a high refractive index layer positioned on top of the substrate, a first low refractive index buffer layer positioned on the waveguide, a metallic layer positioned on the first buffer layer, a high refractive index tuning layer positioned on the metallic layer, and a second low refractive index buffer layer positioned on the tuning layer, at least one light source for propagating light signals through the waveguide, and at least one detector for monitoring output signals from the waveguide.
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27. A surface plasmon sensor apparatus comprising multiple waveguide structures, each waveguide structure further comprising a waveguide having a low refractive index substrate and a high refractive index material deposited on the substrate, a low refractive index buffer layer positioned on the waveguide, a high refractive index tuning layer positioned on the buffer layer, and a metallic layer positioned on the tuning layer, at least one light source for propagating light signals through the waveguide, and at least one detector for monitoring output signals from the waveguide.
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28. A surface plasmon sensor apparatus comprising an optical waveguide, the waveguide having a low refractive index substrate and a high refractive index material deposited on the substrate, at least one low refractive index buffer layer positioned on the waveguide, at least one high refractive index tuning layer positioned above the buffer layers, a metallic layer positioned over the tuning layer layers, and a light source for propagating light signals through the waveguide, and a detector for monitoring output signals from the waveguide.
Specification