Abstract

We demonstrate robust, low bend loss photonic wires made from air-clad microstructured “grapefruit” fiber. By tapering the fiber and collapsing the air-holes, the guided mode evolves from being fully embedded within the fiber to a spatially-localized evanescent regime a few millimeters in length, where the mode is strongly influenced by the external environment. We show that in the embedded regime there is negligible loss when the taper is immersed in index-matching fluid, while in the evanescent regime the attenuation increases by over 35 dB. Furthermore, we show that an 11 µm wire in the embedded regime can be bent to a radius as small as 95 µm with bend-loss of 0.03 dB in a 500 nm band. The combination of spatial localization, strong dependence on the external environment and small bend radius make the device ideally suited for bio-photonic sensing.

© 2005 Optical Society of America

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References

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K. Miyake, M. Hachiwaka, T. Kinoshita, S. Yamaguchi, H. Kubota, and S. Kawanishi. "Bend Resistant Photonic Crystal Fiber Compatible with conventional Single Mode Fiber." in Proceedings of European Conference on Optical Communication, ed. Stockholm, 2004), pp. Mo3.3.4.

J. Lightwave Technol.

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[CrossRef]

Nature

L.M. Tong, R.R. Gattass, J.B. Ashcom, S.L. He, J.Y. Lou, M.Y. Shen, I. Maxwell, and E. Mazur, "Subwavelength-diameter silica wires for low-loss optical wave guiding," Nature 426, 816-819 (2003).
[CrossRef] [PubMed]

Opt. Express

Opt. Lett.

Photon. Tech. Lett.

J.K. Chandalia, B.J. Eggleton, R.S. Windeler, S.G. Kosinski, X. Liu, and C. Xu, "Adiabatic coupling in tapered air-silica microstructured optical fiber," Photon. Tech. Lett. 13, 52-54 (2001).
[CrossRef]

Science

P. Russell, "Photonic crystal fibers," Science 299, 358-362 (2003).
[CrossRef] [PubMed]

Other

OFS Laboratories, 600 Mountain Avenue, Murray Hill, NJ 07974 (2004).

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Figures (7)

Fig. 1.
Fig. 1.

Schematic of: (a) untapered MOF consisting of six air-holes surrounding a Ge-doped core; (b) the MOF tapered by stretching under a brushing flame, while maintaining the air-holes; (c) the local heat-treatment of the tapered MOF, where it is held stationary under a flame, causing the air-holes to collapse.

Fig. 2.
Fig. 2.

(a) Simulated evolution of the field intensity as the core mode propagates through a region where the holes collapse and re-appear. The thin lines represent the outline of the taper and collapsing holes. The plot on the right shows the field intensity distribution of the launched mode. (b) Cross-sectional field intensity distribution at various positions along the taper, as the mode propagates through the heat-treated region.

Fig. 3.
Fig. 3.

Microscope images along an “adiabatic” heat treated Grape fruit fiber taper. (a) Outside of heat treated region (b) transition region where holes are collapsing, and (c) the waist where

Fig. 4.
Fig. 4.

Transmission spectra of tapered MOF relative to the untapered fiber. Prior to heat-treatment, the bare and index-matched tapers have identical spectra. After heat-treatment, when the holes have collapsed, the transmission in the index-matched case is lower by 40–70 dB.

Fig. 5.
Fig. 5.

Measurement of power transmitted through the taper, before and after heat-treatment, with an approximately 300 µm droplet of index-matching fluid is applied at different positions along the taper. The schematic shows the fluid being applied using a SMF.

Fig. 6.
Fig. 6.

Bend loss measurements of untreated MOF taper, in which the taper wound in a loop. Bend loss as a function of bend radius was measured in 500nm power band.

Fig. 7.
Fig. 7.

Bend loss as a function of wavelength for bend radius of 95 µm. Loss due to bending is just discernable for wavelength greater than 1630 nm.

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