Abstract

We present a theoretical study of the ambient refractive index sensing characteristics of long period gratings in bare and metal-coated D-shaped fibers. An equivalent rectangular core waveguide method based on the first-order perturbation theory has been used to study the modal behavior of the waveguide. Power coupling corresponding to dual resonance in both cases has been investigated, and an optimum metal thickness giving maximum sensitivity has been found to exist. The study shows that the dual resonances can be shifted to lower wavelengths by increasing (decreasing) the metal thickness (core to flat surface separation). Further, an optimum combination of metal thickness and core to flat surface separation, corresponding to maximum sensitivity, has been presented for different cladding modes and their relative performance has been discussed. It has been shown theoretically that detection of refractive index changes as small as 1.67×107RIU in the ambient region is possible using the optimized parameters. The study should find application in realizing highly sensitive biochemical sensors.

© 2009 Optical Society of America

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References

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    [CrossRef]
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    [CrossRef]
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    [CrossRef]
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    [CrossRef]
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    [CrossRef]

2008 (1)

2007 (2)

2006 (2)

1999 (3)

X. Shu, S. Zhu, Q. Wang, S. Jiang, W. Shi, Z. Huang, and E. Huang, “Dual resonance peaks of LP cladding mode in long period gratings,” Electron. Lett. 35, 649-650 (1999).
[CrossRef]

X. Shu, X. Zhu, S. Jiang, W. Shi, and D. Huang, “High sensitivity of dual resonant peaks of long-period fiber grating to surrounding refractive index changes,” Electron. Lett. 35, 1580-1581 (1999).
[CrossRef]

X. Shu and D. Huang, “Highly sensitive chemical sensor based on the measurement of the separation of dual resonant peak in a 100 μm-period fiber grating,” Opt. Commun. 171, 65-69(1999).
[CrossRef]

1996 (1)

1984 (1)

A. Kumar and R. K. Varshney, “Propagation characteristics of highly elliptical core optical waveguides: a perturbation approach,” Opt. Quantum Electron. 16, 349-354 (1984).
[CrossRef]

1979 (1)

R. B. Dyott, J. R. Cozens, and D. G. Morris, “Preservation of polarization in optical fiber waveguides with elliptical cores,” Electron. Lett. 15, 380-381 (1979).
[CrossRef]

Adams, M. J.

M. J. Adams, Introduction to Optical Waveguides (Wiley, 1981).

Albert, J.

Bhatia, V.

Cozens, J. R.

R. B. Dyott, J. R. Cozens, and D. G. Morris, “Preservation of polarization in optical fiber waveguides with elliptical cores,” Electron. Lett. 15, 380-381 (1979).
[CrossRef]

Dyott, R. B.

R. B. Dyott, J. R. Cozens, and D. G. Morris, “Preservation of polarization in optical fiber waveguides with elliptical cores,” Electron. Lett. 15, 380-381 (1979).
[CrossRef]

R. B. Dyott, Elliptical Fiber Waveguides (Artech, 1995).

He, Y-J.

Huang, D.

X. Shu, X. Zhu, S. Jiang, W. Shi, and D. Huang, “High sensitivity of dual resonant peaks of long-period fiber grating to surrounding refractive index changes,” Electron. Lett. 35, 1580-1581 (1999).
[CrossRef]

X. Shu and D. Huang, “Highly sensitive chemical sensor based on the measurement of the separation of dual resonant peak in a 100 μm-period fiber grating,” Opt. Commun. 171, 65-69(1999).
[CrossRef]

Huang, E.

X. Shu, S. Zhu, Q. Wang, S. Jiang, W. Shi, Z. Huang, and E. Huang, “Dual resonance peaks of LP cladding mode in long period gratings,” Electron. Lett. 35, 649-650 (1999).
[CrossRef]

Huang, J.-F.

Huang, Z.

X. Shu, S. Zhu, Q. Wang, S. Jiang, W. Shi, Z. Huang, and E. Huang, “Dual resonance peaks of LP cladding mode in long period gratings,” Electron. Lett. 35, 649-650 (1999).
[CrossRef]

Jiang, S.

X. Shu, X. Zhu, S. Jiang, W. Shi, and D. Huang, “High sensitivity of dual resonant peaks of long-period fiber grating to surrounding refractive index changes,” Electron. Lett. 35, 1580-1581 (1999).
[CrossRef]

X. Shu, S. Zhu, Q. Wang, S. Jiang, W. Shi, Z. Huang, and E. Huang, “Dual resonance peaks of LP cladding mode in long period gratings,” Electron. Lett. 35, 649-650 (1999).
[CrossRef]

Kashyap, R.

Kumar, A.

S. M. Tripathi, A. Kumar, E. Marin, and J.-P. Meunier, “Side-polished optical fiber grating-based refractive index sensors utilizing the pure surface plasmon polariton,” J. Lightwave Technol. 26, 1980-1985 (2008).
[CrossRef]

A. Kumar and R. K. Varshney, “Propagation characteristics of highly elliptical core optical waveguides: a perturbation approach,” Opt. Quantum Electron. 16, 349-354 (1984).
[CrossRef]

Lo, Y-L.

Marin,, E.

Meunier, J.-P.

Morris, D. G.

R. B. Dyott, J. R. Cozens, and D. G. Morris, “Preservation of polarization in optical fiber waveguides with elliptical cores,” Electron. Lett. 15, 380-381 (1979).
[CrossRef]

Nemova, G.

Shevchenko, Y. Y.

Shi, W.

X. Shu, S. Zhu, Q. Wang, S. Jiang, W. Shi, Z. Huang, and E. Huang, “Dual resonance peaks of LP cladding mode in long period gratings,” Electron. Lett. 35, 649-650 (1999).
[CrossRef]

X. Shu, X. Zhu, S. Jiang, W. Shi, and D. Huang, “High sensitivity of dual resonant peaks of long-period fiber grating to surrounding refractive index changes,” Electron. Lett. 35, 1580-1581 (1999).
[CrossRef]

Shu, X.

X. Shu, X. Zhu, S. Jiang, W. Shi, and D. Huang, “High sensitivity of dual resonant peaks of long-period fiber grating to surrounding refractive index changes,” Electron. Lett. 35, 1580-1581 (1999).
[CrossRef]

X. Shu and D. Huang, “Highly sensitive chemical sensor based on the measurement of the separation of dual resonant peak in a 100 μm-period fiber grating,” Opt. Commun. 171, 65-69(1999).
[CrossRef]

X. Shu, S. Zhu, Q. Wang, S. Jiang, W. Shi, Z. Huang, and E. Huang, “Dual resonance peaks of LP cladding mode in long period gratings,” Electron. Lett. 35, 649-650 (1999).
[CrossRef]

Tripathi, S. M.

Varshney, R. K.

A. Kumar and R. K. Varshney, “Propagation characteristics of highly elliptical core optical waveguides: a perturbation approach,” Opt. Quantum Electron. 16, 349-354 (1984).
[CrossRef]

Vengsarkar, A. M.

Wang, Q.

X. Shu, S. Zhu, Q. Wang, S. Jiang, W. Shi, Z. Huang, and E. Huang, “Dual resonance peaks of LP cladding mode in long period gratings,” Electron. Lett. 35, 649-650 (1999).
[CrossRef]

Zhu, S.

X. Shu, S. Zhu, Q. Wang, S. Jiang, W. Shi, Z. Huang, and E. Huang, “Dual resonance peaks of LP cladding mode in long period gratings,” Electron. Lett. 35, 649-650 (1999).
[CrossRef]

Zhu, X.

X. Shu, X. Zhu, S. Jiang, W. Shi, and D. Huang, “High sensitivity of dual resonant peaks of long-period fiber grating to surrounding refractive index changes,” Electron. Lett. 35, 1580-1581 (1999).
[CrossRef]

Electron. Lett. (3)

X. Shu, S. Zhu, Q. Wang, S. Jiang, W. Shi, Z. Huang, and E. Huang, “Dual resonance peaks of LP cladding mode in long period gratings,” Electron. Lett. 35, 649-650 (1999).
[CrossRef]

X. Shu, X. Zhu, S. Jiang, W. Shi, and D. Huang, “High sensitivity of dual resonant peaks of long-period fiber grating to surrounding refractive index changes,” Electron. Lett. 35, 1580-1581 (1999).
[CrossRef]

R. B. Dyott, J. R. Cozens, and D. G. Morris, “Preservation of polarization in optical fiber waveguides with elliptical cores,” Electron. Lett. 15, 380-381 (1979).
[CrossRef]

J. Lightwave Technol. (1)

J. Opt. Soc. Am. B (2)

Opt. Commun. (1)

X. Shu and D. Huang, “Highly sensitive chemical sensor based on the measurement of the separation of dual resonant peak in a 100 μm-period fiber grating,” Opt. Commun. 171, 65-69(1999).
[CrossRef]

Opt. Lett. (3)

Opt. Quantum Electron. (1)

A. Kumar and R. K. Varshney, “Propagation characteristics of highly elliptical core optical waveguides: a perturbation approach,” Opt. Quantum Electron. 16, 349-354 (1984).
[CrossRef]

Other (5)

M. J. Adams, Introduction to Optical Waveguides (Wiley, 1981).

E.D.Palik, ed., Handbook of Optical Constants of Solids (Academic, 1985).

R. Kashyap, Fiber Bragg Gratings (Academic, 1999).

J.Homola, ed., Surface Plasmon Resonance Based Sensors (Springer, 2006).
[CrossRef]

R. B. Dyott, Elliptical Fiber Waveguides (Artech, 1995).

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Figures (7)

Fig. 1
Fig. 1

(a) Schematic of the sensor structure and (b) tranverse refractive index profile along the minor axis.

Fig. 2
Fig. 2

Equivalent rectangular core waveguide and the perturbation regions marked by 1–27.

Fig. 3
Fig. 3

Phase matching curves for E 16 Y E 19 Y modes of the bare D-shaped fiber. The ARI has been taken as 1.33.

Fig. 4
Fig. 4

Transmission spectrum of E 19 Y mode at grating periods Λ = 304.3 μm (solid curve) and Λ = 3040.5 μm (dashed curve). The ARI has been taken as 1.33.

Fig. 5
Fig. 5

Variation of fractional modal power in the sensing region ( P se ) with respect to etching depth and metal thickness for the (a)  E 16 Y mode, (b)  E 17 Y mode, (c)  E 18 Y mode, and (d)  E 19 Y mode.

Fig. 6
Fig. 6

Modal field distribution of the E 19 Y mode for different metal thicknesses within the metal and the dielectric regions in the vicinity of it. An enlarged view is shown in the inset.

Fig. 7
Fig. 7

Transmission spectrum of the E 16 Y mode for an ARI of 1.33 (solid curve) and 1.34 (dashed curve) at Λ = 514.3 μm and L = 2 cm .

Tables (1)

Tables Icon

Table 1 Optimized Fiber and Grating Parameters for E 16 Y E 19 Y Cladding Modes and Their Corresponding Sensitivities

Equations (9)

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n ( x , y ) = { n c for     x 2 a 1 2 + y 2 b 1 2 < 1 n icl for     x 2 a 1 2 + y 2 b 1 2 > 1 > x 2 a 2 2 + y 2 b 2 2 n ocl for     x 2 a 2 2 + y 2 b 2 2 > 1 ;       x 2 + y 2 < r 2 ; y c 2 n m for     c 2 < y < d 2 n se for     y > d 2 n air elsewhere .
n 2 ( x , y ) = n 0 2 ( x , y ) + δ n 2 ,
n 0 2 ( x , y ) = n 2 ( x ) + n 2 ( y ) n c 2
n ( x ) = { n c n icl n ocl n air for     | x | e for     e | x | f for     f | x | g for     | x | g , n ( y ) = { n c n icl n ocl n m n se     for     | y | a for     a | y | b for     b y c ; y < c for     c y d for     y d ,
β 2 ( x , y ) = β 0 2 + k 0 2 δ n 2 | Ψ | 2 | Ψ | 2 ,
n 2 ( λ ) 1 = j = 1 3 A j λ 2 λ 2 B j 2 ,
ε ( ω ) = ε [ 1 ω p 2 ω ( ω + i Γ ) ] .
2 π λ R ( n ec n ecl ) + ( κ c κ cl ) = 2 π Λ ,
T = ( δ / α ) 2 sin 2 ( α L ) + cos 2 ( α L ) ,

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