title: Two-photon fluorescence correlation spectroscopy through a dual-clad optical fiber.
abstract: We report on the utilization of a dual-clad optical fiber for two-photon excited fluorescence correlation spectroscopy (FCS). High excitation efficiency is obtained by sending prechirped ultrafast pulses through the single-mode core of the fiber, while the fluorescence collection efficiency is enhanced because of the larger numerical aperture of the inner cladding. We show that the utilization of a dual-clad fiber is critical for ultrasensitive two-photon fluorescence detection. Our system has the ability to detect fluorescent nanospheres as small as 12 nm in radius. Quantum dots of radius 7 nm are also measured and show excellent signal to noise ratio. The particle sizes obtained from the fiber FCS system were confirmed by measurements using a commercial dynamic light scattering (DLS) system.
authors: Center for Ultrafast Optical Science, University of Michigan, 2200 Bonisteel Blvd., Ann Arbor, MI 48109-2099, USA. ycchang@umich.edu
authors: Yu-Chung
authors: YC
authors: Chang
authors: Jing Yong
authors: JY
authors: Ye
authors: Thommey
authors: T
authors: Thomas
authors: Yi
authors: Y
authors: Chen
authors: James R
authors: JR
authors: Baker
authors: Theodore B
authors: TB
authors: Norris
mesh_terms: D004867:Equipment Design; D019544:Equipment Failure Analysis; D005336:Fiber Optic Technology / Q000295:instrumentation*; D036641:Microscopy, Fluorescence, Multiphoton / Q000295:instrumentation*; D049329:Nanostructures / Q000737:chemistry* / Q000648:ultrastructure*; D055100:Optical Fibers; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D013050:Spectrometry, Fluorescence / Q000295:instrumentation*