High-sensitivity near-IR absorption measurements of nanoliter samples in a cavity enhanced fiber sensor

Anthony L. Gomez; Julia A. Fruetel; Ray P. Bambha

doi:10.1117/12.826622

21 August 2009 High-sensitivity near-IR absorption measurements of nanoliter samples in a cavity enhanced fiber sensor

Anthony L. Gomez, Julia A. Fruetel, Ray P. Bambha

Proceedings Volume 7397, Biosensing II; 739706 (2009) https://doi.org/10.1117/12.826622
Event: SPIE NanoScience + Engineering, 2009, San Diego, California, United States

Abstract

A compact fiber optic sensor is described using Incoherent Broad-Band Cavity Enhanced Absorption Spectroscopy for sensitive detection of nanoliter samples of aqueous chemicals and microorganisms in capillaries. Absorption was measured in a 70 μm gap, comparable to the inside diameter of a capillary used for electrophoresis, between the ends of two short segments of multimode fiber. The other ends of the fibers were optically contacted to dielectric mirrors to form an 11-cm cavity resonator. Light from a superluminescent diode (λ=1054 nm, BW=35 nm FWHM) was coupled into one end of the cavity, and transmission through the cavity was measured using a silicon photodiode. Dilute aqueous solutions of near infrared dye were used to determine the minimum detectable absorption change of 4x10^-6 for 10 second integration and unity signal-to-noise ratio, which is approximately two orders of magnitude more sensitive than previously published results for systems with comparable sample path lengths.

Citation Download Citation

Anthony L. Gomez, Julia A. Fruetel, and Ray P. Bambha "High-sensitivity near-IR absorption measurements of nanoliter samples in a cavity enhanced fiber sensor", Proc. SPIE 7397, Biosensing II, 739706 (21 August 2009); https://doi.org/10.1117/12.826622

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