Abstract

A directional coupler switch structure capable of short switching length and wide bandwidth is proposed. The switching length and bandwidth have a trade-off relationship in conventional directional coupler switches. Dispersion curves that avoid this trade-off are derived, and a two-dimensional photonic crystal structure that achieves these dispersion curves is presented. Numerical calculations show that the switching length of the proposed structure is 7.1% of that for the conventional structure, while the bandwidth is 2.17 times larger.

© 2006 Optical Society of America

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References

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  1. Y. Sugimoto, Y. Tanaka, N. Ikeda, K. Kanamoto, Y. Nakamura, S. Ohkouchi, H. Nakamura, K. Inoue, H. Sasaki,Y. Watanabe, K. Ishida, H. Ishikawa and K. Asakawa, “Two dimensional semiconductor-based photonic crystal slab waveguides for ultra-fast optical signal processing devices,” IEICE Transaction on Electronics E87C, 316-327 (2004).
  2. M. Loncar, T. Yoshie, A. Scherer, P. Gogna, and Y. M. Qiu, “ Low-threshold photonic crystal laser,” Appl. Phys. Lett. 81, 2680-2682 (2002).
    [CrossRef]
  3. S. Noda, A. Chutinan and M. Imada, “Trapping and emission of photons by a single defect in a photonic bandgap structure,” Nature 407, 608-610 (2000).
    [CrossRef] [PubMed]
  4. N. Yamamoto, Y. Watanabe and K. Komori, “Design of photonic crystal directional coupler with high extinction ratio and small coupling length,” Jpn. J. Appl. Phys. 44 2575-2578 (2005).
    [CrossRef]
  5. Y. A. Vlasov, N. Moll and S. J. McNab, “Mode mixing in asymmetric double-trench photonic crystal waveguides,” J. Appl. Phys. 95, 4538-4544 (2004).
    [CrossRef]
  6. Y. Sugimoto, Y. Tanaka, N. Ikeda, Y. Nakamura, K. Asakawa and K. Inoue, ”Low propagation loss of 0.76 dB/mm in GaAs-based single-line-defect two-dimensional photonic crystal slab waveguides up to 1 cm in length,” Opt. Express 12, 1090-1096 (2004).
    [CrossRef] [PubMed]
  7. P. I. Borel, A. Harpoth, L. H. Frandsen and M. Kristensen, “Topology optimization and fabrication of photonic crystal structures,” Opt. Express 12 1996-2001 (2004).
    [CrossRef] [PubMed]
  8. J. Yonekura, M. Ikeda, and T. Baba, “Analysis of Finite 2-D Photonic Crystals of Columns and Lightwave Devices Using the Scattering Matrix Method”, IEEE J. Lightwave Technol. 17 1500-1508 (1999).
    [CrossRef]
  9. S. Boscolo, M. Midrio and C. G. Someda, “Coupling and Decoupling of Electromagnetic Waves in Parallel 2-D Photonic Crystal Waveguides,” IEEE J. Quantum Electron. 38 47-53 (2002).
    [CrossRef]
  10. A. Martinez, F. Cuesta, and J. Marti, “Ultrashort 2-D Photonic Crystal Directional Couplers,” IEEE Photonics Technl. Lett. 15 694-696 (2003).
    [CrossRef]
  11. Y. Tanaka, H. Nakamura, Y. Sugimito, N. Ikeda, K. Asakawa, and K. Inoue, “Coupling Properties in a 2-D Photonic Crystal Slab Directional Coupler With a Triangular Lattice of Air Holes,” IEEE J. Quantum Electron. 41 76-84 (2005).
    [CrossRef]
  12. F. Cuesta-Soto, B. García-Baños, and J. Martí “Compensating intermodal dispersion in photonic crystal directional couplers,” Opt. Lett. 30, 3156-3158 (2005).
    [CrossRef] [PubMed]
  13. H. Nakamura, S. Kohmoto, N. Carlsson, Y. Sugimoto, and K. Asakawa, “Large enhancemnet of optical nonlinearity using quantum dots embedded in a photonic crystal structure for all-optical switch applications,” in Proceedings of IEEE/LEOS the 13th Annual Conference (Institute of Electrical and Electronics Engineers, New York, 2000), pp. 488-489.
  14. N. Yamamoto, J. Sugisaka, S. H. Jeong, and K. Komori, unpublished.

Appl. Phys.Lett.

M. Loncar, T. Yoshie, A. Scherer, P. Gogna, and Y. M. Qiu, “ Low-threshold photonic crystal laser,” Appl. Phys. Lett. 81, 2680-2682 (2002).
[CrossRef]

IEEE J. Lightwave Technol.

J. Yonekura, M. Ikeda, and T. Baba, “Analysis of Finite 2-D Photonic Crystals of Columns and Lightwave Devices Using the Scattering Matrix Method”, IEEE J. Lightwave Technol. 17 1500-1508 (1999).
[CrossRef]

IEEE J. Quantum Electron.

S. Boscolo, M. Midrio and C. G. Someda, “Coupling and Decoupling of Electromagnetic Waves in Parallel 2-D Photonic Crystal Waveguides,” IEEE J. Quantum Electron. 38 47-53 (2002).
[CrossRef]

Y. Tanaka, H. Nakamura, Y. Sugimito, N. Ikeda, K. Asakawa, and K. Inoue, “Coupling Properties in a 2-D Photonic Crystal Slab Directional Coupler With a Triangular Lattice of Air Holes,” IEEE J. Quantum Electron. 41 76-84 (2005).
[CrossRef]

IEEE Photonics Technl. Lett.

A. Martinez, F. Cuesta, and J. Marti, “Ultrashort 2-D Photonic Crystal Directional Couplers,” IEEE Photonics Technl. Lett. 15 694-696 (2003).
[CrossRef]

IEICE Transaction on Electronics

Y. Sugimoto, Y. Tanaka, N. Ikeda, K. Kanamoto, Y. Nakamura, S. Ohkouchi, H. Nakamura, K. Inoue, H. Sasaki,Y. Watanabe, K. Ishida, H. Ishikawa and K. Asakawa, “Two dimensional semiconductor-based photonic crystal slab waveguides for ultra-fast optical signal processing devices,” IEICE Transaction on Electronics E87C, 316-327 (2004).

J. Appl. Phys.

Y. A. Vlasov, N. Moll and S. J. McNab, “Mode mixing in asymmetric double-trench photonic crystal waveguides,” J. Appl. Phys. 95, 4538-4544 (2004).
[CrossRef]

Jpn. J. Appl. Phys.

N. Yamamoto, Y. Watanabe and K. Komori, “Design of photonic crystal directional coupler with high extinction ratio and small coupling length,” Jpn. J. Appl. Phys. 44 2575-2578 (2005).
[CrossRef]

Nature

S. Noda, A. Chutinan and M. Imada, “Trapping and emission of photons by a single defect in a photonic bandgap structure,” Nature 407, 608-610 (2000).
[CrossRef] [PubMed]

Opt. Express

Opt. Lett.

Proc. Institute of Electrical and Electronics Engineers 2000

H. Nakamura, S. Kohmoto, N. Carlsson, Y. Sugimoto, and K. Asakawa, “Large enhancemnet of optical nonlinearity using quantum dots embedded in a photonic crystal structure for all-optical switch applications,” in Proceedings of IEEE/LEOS the 13th Annual Conference (Institute of Electrical and Electronics Engineers, New York, 2000), pp. 488-489.

Other

N. Yamamoto, J. Sugisaka, S. H. Jeong, and K. Komori, unpublished.

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Figures (6)

Fig. 1.
Fig. 1.

Schematics of our considering ring buffer device. It consists of an directional coupler switch as an input- and output-port and an ring shape waveguide to store the optical pulses.

Fig. 2.
Fig. 2.

Schematic of directional coupler switch. In white region of which length is L fix, optical parameters are fixed. In gray region of which length is L sw, the wavenumbers of each eigen modes will be changed from k e and k o to ke and ko respectively by switching operation such as change of refractive index.

Fig. 3.
Fig. 3.

Schematic of ideal dispersion curve for small switching length and wide bandwidth. Blue lines are even modes and red lines are odd modes. Solid lines and dashed lines are the dispersion curves at switch-off and switch-on condition, respectively. f n is the operating frequency which should be between the flat frequency region of even modes before and after the switching operation.

Fig. 4.
Fig. 4.

Dispersion curves and energy distributions of parallel photonic crystal waveguides consisting of uniform holes arranged in a triangular lattice. The field distribution of even mode around the wavenumber marked by circle is spread into center hole array. On the other hand, the field of another are concentrated nearby waveguides.

Fig. 5.
Fig. 5.

(a) The directional coupler structure to realize flat frequency region. The radiuses of the air holes of center and outside of waveguides are enlarged to 0.445a and 0.33a respectively. (The radiuses of the another air holes are 0.29a.) And the position of the air holes of outside of waveguides are shifted 0.213a towards the center of the structure. (b) The dispersion curves of the structure shown in Fig. 5(a). The even mode have flat frequency region.

Fig. 6.
Fig. 6.

Switching lengths and bandwidths of directional coupler switch: (a) proposed structure and (b) conventional structure. Solid lines denote switching length, and dashed lines denote bandwidth.

Tables (1)

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Table 1. Minimum switching lengths and bandwidths for various refractive index changes

Equations (8)

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( k e k o ) L c = ( 2 n + 1 ) π
( k e , fix k o , fix ) L fix + ( k e , off k o , off ) L sw = ( 2 n + 1 ) π , and
( k e , fix k o , fix ) L fix + ( k e , on k o , on ) L sw = 2 ,
L sw = ( 2 n + 1 ) π ( k e , on k e , off ) ( k o , on k o , off )
dk = 1 ω k ω n dn .
L sw ( 2 n + 1 ) π 1 ω e k ω e n dn + 1 ω o k ω o n dn
( 2 n + 1 ) π ( 1 ω e k + 1 ω o k ) ω n dn .
Δ ω = Δϕ ( 1 ω e , fix k 1 ω o , fix k ) L fix + ( 1 ω e , off k 1 ω o , off k ) L sw .

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