Optical sensor employing a refractive index engineered metal oxide material

Abstract

An optical sensor device includes an optical waveguide portion having a core, the core having a first refractive index, and a functional material layer coupled to the optical fiber portion, the functional material layer being made of a metal oxide material, the functional material layer being structured to have a second refractive index, the second refractive index being less than the first refractive index. The functional material layer may be a nanostructure material comprising the metal oxide material with a plurality of holes or voids formed therein such that the functional material layer is caused to have the second refractive index.

What is claimed is: 
     
         1 . An optical sensor device, comprising:
 an optical waveguide portion having a core, the core having a first refractive index; and   a functional material layer coupled to the optical waveguide portion, wherein the functional material layer comprises a metal oxide material, the functional material layer being structured to have a second refractive index, the second refractive index being less than the first refractive index.   
     
     
         2 . The optical sensor device according to  claim 1 , wherein the functional material layer comprises a coating layer provided on a surface of the optical waveguide portion. 
     
     
         3 . The optical sensor device according to  claim 2 , wherein the optical waveguide portion is a D-shaped optical fiber having a cladding layer having a hemispherical cross-section, the core being provided at least in part within the cladding layer, the coating layer being provided on a top, flat surface of the cladding layer and a top portion of the core. 
     
     
         4 . The optical sensor device according to  claim 3 , further comprising an in-fiber optic component formed in the core. 
     
     
         5 . The optical sensor device according to  claim 4 , wherein the in-fiber optic component is a Fiber Bragg Grating (FBG). 
     
     
         6 . The optical sensor device according to  claim 1 , wherein the functional material layer is a nanostructure material comprising the metal oxide material with a plurality of voids termed therein such that the functional material layer is caused to have the second refractive index. 
     
     
         7 . The optical sensor device according to  claim 6 , wherein the voids comprise about 60% of the nanostructure material causing the functional material layer to have a total volume fraction of voids of about 60%. 
     
     
         8 . The optical sensor device according to  claim 7 , wherein the voids are spherical and each have a diameter of 100 nm or less. 
     
     
         9 . The optical sensor device according to  claim 8 , wherein the voids are spherical and each have a diameter of about 10 nm to about 20 nm. 
     
     
         10 . The optical sensor device according to  claim 6 , wherein the second refractive index is about 99.0% to about 99.7% of the first refractive index. 
     
     
         11 . The optical sensor device according to  claim 6 , wherein the metal oxide in a bulk, fully dense form without the voids has a third refractive index greater than the first refractive index. 
     
     
         12 . The optical sensor device according to  claim 6 , wherein the nanostructure material is formed using a sol-gel method. 
     
     
         13 . The optical sensor device according to  claim 12 , wherein the sol-gel method uses a triblock copolymer as a structure directing agent. 
     
     
         14 . The optical sensor device according to  claim 13 , wherein the triblock copolymer is poloxamer 407. 
     
     
         15 . The optical sensor device according to  claim 13 , wherein in the sol-gel method the structure directing agent is mixed with SnCl 4  in Ethanol to form a precursor, the precursor is modified by addition of HCl and then heated. 
     
     
         16 . The optical sensor device according to  claim 1 , wherein the metal oxide material is selected from a group consisting of a zeolite, SnO 2 , TiO2, ZnO, WO 3 , and a perovskite. 
     
     
         17 . The optical sensor device according to  claim 1 , wherein the functional material layer is porous. 
     
     
         18 . A method of making an optical sensor device, comprising:
 providing an optical waveguide portion having a core; and   forming a functional material layer made of a metal oxide material, the functional material layer being coupled to the optical waveguide portion, the core having a first refractive index, the functional material layer being structured to have a second refractive index, the second refractive index being less than the first refractive index.   
     
     
         19 . The method according to  claim 18 , wherein the functional material layer is porous. 
     
     
         20 . The method according to  claim 19 , wherein the functional material layer is a nanostructure material comprising the metal oxide material with a plurality of voids formed therein such that the functional material layer is caused to have the second refractive index. 
     
     
         21 . The method according to  claim 19 , wherein the voids comprise about 60% of the nanostructure material causing the functional material layer to have a total volume fraction of voids of about 60%. 
     
     
         22 . The method according to  claim 20 , wherein the voids are spherical and each have a diameter of 100 nm or less. 
     
     
         23 . The method according to  claim 22 , wherein the voids are spherical and each have a diameter of about 10 nm to about 50 nm. 
     
     
         24 . The method according to  claim 18 , wherein the second refractive index is about 99.0% to about 99.7% of the first refractive index. 
     
     
         25 . The method according to  claim 20 , wherein the metal oxide in a bulk, fully dense form without the voids has a third refractive index greater than the first refractive index. 
     
     
         26 . The method according to  claim 18 , wherein the step of forming the functional material layer employs a sol-gel method. 
     
     
         27 . The method according to  claim 26 , wherein the step of forming the functional material layer includes mixing a structure directing agent with a first compound in an alcohol or another solvent to form a precursor, modifying the precursor by addition of a second compound to form a modified precursor, and heating the modified precursor to form a heated modified precursor, wherein the functional material layer is formed using the precursor. 
     
     
         28 . The method according to  claim 27 , wherein the first compound is SnCl 4  wherein the alcohol is ethanol, and wherein the second compound is 37% HCl in water. 
     
     
         29 . The method according to  claim 27 , wherein the structure directing agent is a triblock copolymer. 
     
     
         30 . The method according to  claim 29 , wherein the triblock copolymer is poloxamer 407. 
     
     
         31 . An optical sensor device, comprising:
 a multilayer hollow waveguide device having:
 a hollow waveguide tube layer, 
 an intermediate layer provided inside the hollow waveguide tube layer; and 
 a metal oxide coating layer inside the intermediate layer. 
   
     
     
         32 . The optical sensor device according to  claim 31 , wherein the intermediate layer is a reflective coating layer 
     
     
         33 . The optical sensor device according to  claim 32 , wherein the reflective coating layer is provided directly on an inner surface of the hollow waveguide tube layer. 
     
     
         34 . The optical sensor device according to  claim 32 , wherein the metal oxide coating layer is provided directly on an inner surface of the reflective coating layer. 
     
     
         35 . The optical sensor device according to  claim 32 , wherein the reflective coating layer is a metal coating layer. 
     
     
         36 . The optical sensor device according to  claim 31 , wherein the hollow waveguide tube layer is made of silica, plastic or metal. 
     
     
         37 . The optical sensor device according to  claim 31 , wherein the hollow waveguide tube layer has a first refractive index, wherein the intermediate layer is a guiding layer having a second refractive index that is greater than the first refractive index, and the metal oxide coating layer is structured to have a third refractive index, the third refractive index being less than the second refractive index.