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Applied Optics

Applied Optics


  • Editor: Glenn D. Boreman
  • Vol. 44, Iss. 34 — Dec. 1, 2005
  • pp: 7270–7274

Characterization of gradient-index lens-fiber spacing toward applications in two-photon fluorescence endoscopy

Ling Fu, Xiaosong Gan, and Min Gu  »View Author Affiliations

Applied Optics, Vol. 44, Issue 34, pp. 7270-7274 (2005)

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We report on the experimental investigation into the characterization of two-photon fluorescence microscopy based on the separation distance of a single-mode optical fiber coupler and a gradient-index (GRIN) rod lens. The collected two-photon fluorescence signal exhibits a maximum intensity at a defined separation distance (gap length) where the increasing effective excitation numerical aperture is balanced by the decreasing confocal emission collection. A maximum signal is found at gap lengths of approximately 2, 1.25, and 1.75 mm for GRIN lenses with pitches of 0.23, 0.25, and 0.29 wavelength at 830 nm. The maximum two-photon fluorescence signal collected corresponds to a threefold reduction of axial resolution (38.5 µm at 1.25 mm), compared with the maximum resolution (11.6 µm at 5.5 mm), as shown by the three-dimensional imaging of 10 µm beads. These results demonstrate an intrinsic trade-off between signal collection and axial resolution.

© 2005 Optical Society of America

OCIS Codes
(110.2350) Imaging systems : Fiber optics imaging
(180.2520) Microscopy : Fluorescence microscopy

ToC Category:
Imaging Systems

Original Manuscript: January 10, 2005
Revised Manuscript: May 20, 2005
Manuscript Accepted: May 31, 2005
Published: December 1, 2005

Virtual Issues
Vol. 1, Iss. 1 Virtual Journal for Biomedical Optics

Ling Fu, Xiaosong Gan, and Min Gu, "Characterization of gradient-index lens-fiber spacing toward applications in two-photon fluorescence endoscopy," Appl. Opt. 44, 7270-7274 (2005)

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  1. E. B. Brown, R. B. Campbell, Y. Tsuzuki, L. Xu, P. Carmeliet, D. Fukumura, R. K. Jain, “In vivo measurement of gene expression, angiogenesis and physiological function in tumors using multiphoton laser scanning microscopy,” Nat. Med. 7, 864–868 (2001). [CrossRef] [PubMed]
  2. C. Stosiek, O. Garaschuk, K. Holthoff, A. Konnerth, “In vivo two-photon calcium imaging of neuronal networks,” Proc. Natl. Acad. Sci. 100, 7319–7324 (2003).
  3. W. Denk, J. H. Strickler, W. W. Webb, “Two-photon laser scanning fluorescence microscopy,” Science 248, 73–75 (1990). [CrossRef] [PubMed]
  4. W. R. Zipfel, R. M. Williams, W. W. Webb, “Nonlinear magic: multiphoton microscopy in the biosciences,” Nat. Biotech. 21, 1369–1377 (2003). [CrossRef]
  5. J. C. Jung, M. J. Schnitzer, “Multiphoton endoscopy,” Opt. Lett. 28, 902–904 (2003). [CrossRef] [PubMed]
  6. D. Bird, M. Gu, “Two-photon fluorescence endoscopy with a micro-optic scanning head,” Opt. Lett. 28, 1552–1554 (2003). [CrossRef] [PubMed]
  7. J. Knittel, L. Schnieder, G. Buess, B. Messerschmidt, T. Possner, “Endoscope-compatible confocal microscope using a gradient index-lens system,” Opt. Commun. 188, 267–273 (2001). [CrossRef]
  8. D. Bird, M. Gu, “Fiber-optic two-photon scanning fluorescence microscopy,” J. Microsc. 208, 35–48 (2002). [CrossRef] [PubMed]
  9. D. Bird, M. Gu, “Compact two-photon fluorescence microscope based on a single-mode fiber coupler,” Opt. Lett. 27, 1031–1033 (2002). [CrossRef]
  10. B. E. A. Saleh, M. C. Teich, Fundamentals of Photonics (Wiley, New York, 1991). [CrossRef]
  11. M. Gu, Principles of Three-Dimensional Imaging in Confocal Microscopes (World Scientific, Singapore, 1996).
  12. C. Xu, W. W. Webb, “Measurement of two-photon excitation of cross sections of molecular fluorophores with data from 690 to 1050 nm,” J. Opt. Soc. Am. B 13, 481–491 (1996). [CrossRef]
  13. M. Gu, C. J. R. Sheppard, “Signal level of the fiber-optical confocal scanning microscope,” J. Mod. Opt. 38, 1621–1630 (1991). [CrossRef]
  14. M. Gu, D. Bird, “Three-dimensional optical-transfer-function analysis of fiber-optical two-photon fluorescence microscopy,” J. Opt. Soc. Am. A 20, 941–947 (2003). [CrossRef]

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