Abstract

We propose and numerically investigate the operation of a novel class of polarization-independent splitters based on the photonic crystal fiber (PCF) technology. The proposed polarization-independent feature of the PCF splitter is realized by uniformly distributed elliptically-shaped airholes in the cladding of a dual-core PCF. The design procedure follows a rigorous synthesis protocol based on exact equations for describing the wavelength de-coupling mechanism, and on full-vectorial finite element as well as beam propagation methods for optical characterization of PCFs. The compact de-coupling lengths as well as the low cross-talk over appreciable optical bandwidths are the main advantages of the proposed PCF splitter. The proposed device can be employed in reconfigurable optical communication systems for performing wavelength de-multiplexing operation, especially for fiber-to-the-home applications, as well as the emerging passive optical network applications.

© 2005 Optical Society of America

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References

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    [CrossRef]
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    [CrossRef] [PubMed]
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Electron. Lett. (1)

B. J. Mangan, J. C. Knight, T. A. Birks, P. St. J. Russel, and A. H. Greenway, �??Experimental study of dual core photonic crystal fiber,�?? Electron. Lett. 36, 1358-1359 (2000).
[CrossRef]

IEEE J. Quantum Electron. (1)

R. A. Forber and E. Marom, �??Symmetric directional coupler switches,�?? IEEE J. Quantum Electron. QE-38, 911-919 (1986).
[CrossRef]

IEEE J. Quantum Elencron (1)

K. Saitoh and M. Koshiba, �??Full-vectorial imaginary-distance beam propagation method based on a finite element scheme: application to photonic crystal fibers,�?? IEEE J. Quantum Elencron. 38, 927-933 (2002).
[CrossRef]

IEEE Photonics Technol. Lett. (3)

W. Chi, C. Rolland, F. Shepherd, C. Larocque, N. Puetz, K. D. Chi, and J. M. Xu, �?? InGaAsP/InP vertical directional coupler filter with optimally designed wavelength tunability,�?? IEEE Photonics Technol. Lett. 4, 457-459 (1993).

C. R. Doerr, R. Pafchek, and L. W. Stulz, �??Integrated band demultiplexer using waveguide grating routers,�?? IEEE Photonics Technol. Lett. 15, 1088-1090 (2003).
[CrossRef]

B. J. Offrein, G. L. Bona, F. Horst, W. M. Salemink, R. Beyeler, and R. Germann, �??Wavelength tunable optical add-after-drop filter with flat passband for WDM networks,�?? IEEE Photonics Technol. Lett. 11, 239-241 (1999).
[CrossRef]

J. Lightwave Technol. (3)

Nature (1)

J. C. Knight, �??Photonic crystal fibers,�?? Nature 424, 847-851 (2003).
[CrossRef] [PubMed]

Opt. Express (2)

Opt. Fiber Technol. (1)

J. Broeng, D. Mogilevtsev, S. E. Barkou, and A. Bjarklev, �??Photonic crystal fibers: A new class of optical waveguides,�?? Opt. Fiber Technol. 5, 305-330 (1999).
[CrossRef]

Opt. Lett. (4)

J. C. Knight, T. A. Birks, P. St J. Russell, and J. P. de Sandro, �??Properties of photonic crystal fiber and the effective index model,�?? Opt. Lett. 15, 748-752 (1998).

S. G. Leon-Saval, T. A. Birks, N.Y. Joly, A. K. George, W. J. Wadsworth, G. Kakarantzas, and P.St.J. Russel, �??Splice-free interfacing of photonic crystal fibers,�?? Opt. Lett. 30, 1629-1631 (2005).
[CrossRef] [PubMed]

N. A. Issa, M. A. Eijkelenborg, M. Fellew, F. Cox, G. Henry, and C. J. Large, �??Fabrication and study of microstructured optical fibers with elliptical holes,�?? Opt. Lett. 29, 1336-1338 (2004).
[CrossRef] [PubMed]

J. C. Knight, T. A. Birks, P.St.J. Russel, and D. M. Atkin, �??All-silica single-mode optical fiber with photonic crystal cladding,�?? Opt. Lett. 21, 484-485 (1996).
[CrossRef]

Other (2)

J. A. Buck, Fundamentals of Optical Fibers, Wiley-Interscience (2004).

J. D. Joannopoulos, R. D. Meade, and J. N. Winn, Photonic Crystals: Molding the Flow of Light. (Princenton, NJ: Princeton Univ. Press, 1995).

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Figures (5)

Fig. 1.
Fig. 1.

Topology of a dual-core PCF splitter with uniformly distributed elliptical air-holes in a hexagonal arrangement with pitch number Λ and ellipticity e=dy /dx . By a judicious choice of the geometrical parameters, this PCF structure can exhibit polarization-independent propagation characteristics, at two different wavelength bands.

Fig. 2.
Fig. 2.

Coupling length ratios as functions of the dimensionless parameter dx /Λ, for various values of the hole-ellipticity e=dy /dx , at (a) λ2 = 1.55 μm, (b) at λ1 = 1.3 μm, and (c) for x-polarization at wavelengths λ1, λ2.

Fig. 3.
Fig. 3.

Normalized power distribution in the PCF-splitter for x-polarization (red line), y-polarization (blue line) at wavelengths of (a) λ = 1.3 μm, and (b) λ = 1.55 μm. The coupling length was confirmed by the BPM analysis to be L = 15.4 mm.

Fig. 4.
Fig. 4.

Electric field distributions in the polarization-independent dual core PCF splitter with elliptical air-holes for (a) x-polarization ( Ex ) at λ=1.3 μm and z = 0 mm, (b) x-polarization ( Ex ) at λ=1.3 μm and z = 15.4 mm, (c) y-polarization ( Ey ) at λ=1.3 μm and z = 0 mm, (d) y-polarization ( Ey ) at λ=1.3 μm and z = 15.4 mm, (e) x-polarization ( Ex ) at λ=1.55 μm and z = 0 mm, (f) x-polarization ( Ex ) at λ=1.55 μm and z = 15.4 mm, (g) y-polarization ( Ey ) at λ=1.55 μm and z = 0 mm, and (h) y-polarization ( Ey ) at λ=1.55 μm and z = 15.4 mm.

Fig. 5
Fig. 5

Crosstalk between the two cores of the PCF, and the available optical bandwidths defined at a level of -20 dB for (a) λ d = 1.55 μm, with BW=5.1 nm and (b) λ d = 1.3 μm, with BW=2.7 nm.

Equations (8)

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P out , A = P in cos 2 ( π 2 z L c ) ,
P out , B = P in sin 2 ( π 2 z L c ) ,
L c x , y ( λ ) = λ 2 ( n even x , y n odd x , y ) .
L = mL c x ( λ 1 ) = ( m + q ) L c y ( λ 1 ) = ( m + q ) L c x ( λ 2 ) = ( m + p + q ) L c y ( λ 2 )
L c x ( λ ) L c y ( λ ) = n even y n odd y n even x n odd x ,
L c x ( 1.3 μm ) L c y ( 1.3 μm ) = 9 7 , L c x ( 1.55 μm ) L c y ( 1.55 μm ) = 9 7 , L c x ( 1.3 μm ) L c x ( 1.55 μm ) = 2 1 .
m p q q ( 7,7,2,4 )
Crosstalk j = 10 log 10 [ P j ( λ u ) P x 2 ( λ d ) + P y 2 ( λ d ) ] [ dB ] , j = x or y polarization

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