US 4,650,329 A · Optical 3-d signature device for detecting chemical agents

Abstract

An optical device for obtaining a 3-dimensional signature or a plurality of 2-dimensional signatures for a given sample in order to detect predetermined chemical agents. The device comprises a light channel with a first sensing optical fiber with a coating thereon which changes its absorptive and refractive properties in the presence of a predetermined chemical agent, and a second light channel with a reference optical fiber isolated from the sample. A scanning monochromator is utilized to apply light beams to the sensing and reference fibers, and an optical detector is used to cross-correlate the outputs from the sensing and reference fibers. A variable optical delay line is disposed in one of the fiber channels in order to scan from 0.degree. to 360.degree. in phase shift for each light frequency. A 2-dimensional cross-correlation is obtained for this scan at this frequency. The scanning monochromator is set to run through a series of light frequencies in a given bandwidth. A 2-dimensional cross-correlation phase scan is obtained at each different light frequency. A 3-dimensional cross-correlation may then be obtained (cross-correlation value vs frequency vs phase delay) to provide a signature for a given sample which can be compared to known samples. The device may utilize separate channel bandwidth filters to obtain squeezed states and high S/N ratios.

Claims30

Dependent claims

An optical detection device for chemical agents comprising:

a first optical waveguide with a first coating disposed therearound, said coating have the characteristics of changing its optical properties in the presence of predetermined chemical agents, thereby affecting at least one parameter of light propagating through said first optical waveguide, said first optical waveguide being disposed in a location to detect predetermined chemical agents;
a reference optical waveguide;
means for isolating said reference optical waveguide from exposure to said chemical agents;
means for directing a coherent light beam at a particular frequency into said first and reference optical waveguides to propagate therethrough to provide first and reference light outputs, respectively;
a first variable optical delay line disposed in one of said first or reference optical waveguides for delaying the light propagating therein by a predetermined delay;
means for varying said predetermined delay through a predetermined degree range of phase shift for said particular frequency directed into said first and reference optical waveguides;
and
means for detecting a cross-correlation of said first and reference light outputs to thereby obtain a precise signature characterized by increased signal-to-noise ratio of said light outputs due to a squeezed state relation of two photons emerging from the respective waveguides.

5 more elements

A method for optically detecting chemical agents by obtaining a precise chemical agent signature in a device including a first optical waveguide with a first coating therein which has the property of changing its refractive index and absorption spectrum in the presence of predetermined chemical agents, thereby affecting at least one parameter of light propagating through said first optical waveguide, said first optical waveguide being disposed in a location to detect predetermined chemical agents, and a reference optical waveguide isolated from exposure to chemical agents, comprising the steps of:

exposing said first coating of said first optical waveguide to a sample possibly containing predetermined chemical agents;
directing a coherent light beam at a particular frequency into said first and reference optical waveguides to propagate therethrough to provide a first and a reference light outputs, respectively;
delaying the light beam propagating in either said first or said reference optical waveguides by a predetermined delay, with said predetermined delay being varied through a predetermined degree range of phase shift for said particular frequency directed into said first and reference optical waveguides;
determining a cross-correlation of said first and reference light outputs over said predetermined degree range of delay variation;
and
repeating said directing, delaying and cross-correlation determining steps for each new particular frequency directed into said first and reference optical waveguides to thereby obtain a precise cross-correlation signature characterized by increased signal-to-noise ratio of said light outputs due to a squeezed state relation of two photons emerging from the respective waveguides.

3 more elements

Dependencies are inferred from the claim text.

Optical 3-d signature device for detecting chemical agents

Life of this patent

Optical 3-d signature device for detecting chemical agents

Life of this patent

Abstract

Claims30