We examine the limit of spatial resolution achievable when a single optical fiber is used for excitation and collection of fluorescence from a bulk specimen. We calculate the probability of detecting a fluorescent particle as a function of its position relative to the fiber face, using excitation wavelength λ, radius a, numerical aperture N.A., and the particle’s fluorescence and absorbance spectra. Treating Rhodamine B as a model fluorescent analyte and using appropriate fiber parameters, we show that the maximum axial resolution (defined as the axial distance in a homogenous solution within which 50% of the detected signal originates) achievable is ∼10 μm. We experimentally measured the axial resolution for a 500-μM aqueous solution of Rhodamine B with λ = 543 nm, <i>a</i> = 1.31 μm, and a N.A. of 0.16 and found good qualitative agreement with the calculation.
© 2003 Optical Society of America
(060.0060) Fiber optics and optical communications : Fiber optics and optical communications
(060.2370) Fiber optics and optical communications : Fiber optics sensors
(180.0180) Microscopy : Microscopy
(180.2520) Microscopy : Fluorescence microscopy
J. Balaji, Kanchan Garai, Subhasis Chakrabarti, and Sudipta Maiti, "Axial Resolution Limit of a Fiber-Optic Fluorescence Probe," Appl. Opt. 42, 3780-3784 (2003)