Method and apparatus for enhanced evanescent fluorescence and color filtering using a high refractive index thin film coating

Patent · Mon Jan 01 04:00:00 EST 2001

OSTI ID:873556

Kao, Hung Pin ^[1]; Schoeniger, Joseph ^[2]; Yang, Nancy ^[3]

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1. 2124 Promontory Cir., San Ramon, CA 94583
2. 126 Echo Ave., Oakland, CA 94611
3. 72 Bacon Ct., Lafayette, CA 94549

A technique for increasing the excitation and collection of evanescent fluorescence radiation emanating from a fiber optic sensor having a high refractive index (n.sub.r), dielectric thin film coating has been disclosed and described. The invention comprises a clad optical fiber core whose cladding is removed on a distal end, the distal end coated with a thin, non-porous, titanium dioxide sol-gel coating. It has been shown that such a fiber will exhibit increased fluorescence coupling due in part by 1) increasing the intensity of the evanescent field at the fiber core surface by a constructive interference effect on the propagating light, and 2) increasing the depth of penetration of the field in the sample. The interference effect created by the thin film imposes a wavelength dependence on the collection of the fluorescence and also suggests a novel application of thin films for color filtering as well as increasing collected fluorescence in fiber sensors. Collected fluorescence radiation increased by up to 6-fold over that of a bare fused silica fiber having a numerical aperture (N.A.) of O.6.

• Research Organization: SANDIA CORP
• DOE Contract Number: AC04-94AL85000
• Assignee: Kao, Hung Pin (2124 Promontory Cir., San Ramon, CA 94583);Schoeniger, Joseph (126 Echo Ave., Oakland, CA 94611);Yang, Nancy (72 Bacon Ct., Lafayette, CA 94549)
• Patent Number(s): US 6188812
• OSTI ID: 873556
• Country of Publication: United States
• Language: English

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/385/356/
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cladding
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color
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comprises
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depth
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dielectric
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light
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numerical
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optic
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