American Research Corporation of Virginia

Peter Lo

Howard P Groger

Martin Weiss

Russell J Churchill

Shufang Luo

Bruce L Thomas

Peter Zory

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.

Chemical detector employing surface plasmon resonance excited using an

A chemical sensor uses a semiconductor diode laser having a surface active region. A laser structure, including an active layer, a cladding layer, a barrier layer and a grating layer, is constructed on a substrate. A contact layer is deposited on a surface of the laser structure. One or more electrodes are positioned on the contact layer. A segmented electrode has a first contact pad, a second contact pad, and a surface active region between the first and second pads. A surface active region is created between the two electrodes. The tail of the lasing signal interacts with surface features of the diode laser or with chemical materials or probes in contact with the surface of the diode laser or in contact with coatings on the surface of the diode laser. Chemical changes in the ambient environment induce changes in the laser signal. The modified laser signal output is detected by a detector region integral with or separated from the laser structure. The laser diode sensor has applications in fields involving chemical sensing and identification, including automotive, environmental and medical fields.

Laser diode sensor

A fluorescent sensor for chemical analysis has a light source, an optical waveguide, and a detector. Fluorophores are associated with the optical waveguide. When an impervious waveguide is used, a fluorophore-containing layer is applied to a surface of the waveguide. The fluorophores are excited by a laser, a light emitting diode, an electroluminescent source or a lamp source emitting light propagating at angles to the waveguide. The light source is modulated. A mirror can be used to direct the light beam. The angle of light incidence on the waveguide can be altered by moving the waveguide itself. The waveguide traps the laser-induced fluorescence and projects fluorescence signals through a suitable filter to a photodetector or otherwise wavelength-specific photodetector positioned near the waveguide structure. Remote operation of the sensor is achieved using optical fibers. Patterned waveguides allow multiple excitation sources to illuminate multiple fluorescent probe materials. The change in fluorescence from each fluorophore is sensed as a vector response which is evaluated using digital signal processing. The sensor uses steady state fluorescence and fluorescence decay information to determine identity and concentration of analytes of interest. The invention is used for chemical analysis of gases or of liquid materials.

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Blacksburg, VA, United States of America

Peter Lo