Abstract

High transmission of slow-light in a photonic crystal (PC) waveguide (WG) using a hetero group-velocity (Ht-Vg) PC-WG was proposed and experimentally investigated. The Ht-Vg WG, which comprises a low-group-velocity (L-Vg) PC-WG section between two identical high-group-velocity (H-Vg) PC-WGs, is designed to decrease the impedance mismatch of the L-Vg PC-WG. The increase in transmittance of a propagating pulse was confirmed in the Ht-Vg PC-WG even in the vicinity of the band-gap, whereas the homogeneous PC-WG showed a gradual decrease in transmittance with the pulse wavelength approaching the band-gap. The group index (ng) of the L-Vg region in the Ht-Vg PC-WG was measured by the cross-correlation method and attained a value above 20. On the other hand, the transmittance of the Ht-Vg structure recovered approximately 16dB compared to the homogeneous L-Vg WG having same ng, 17. This recovery is mainly dominated by the coupling improvement due to the Ht-Vg structure, around 12dB. These results indicate the effectiveness of the Ht-Vg structure to use slow light in a PC-WG, which leads to various applications in PC-based optical devices.

© 2007 Optical Society of America

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References

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2006 (3)

K. Asakawa, Y. Sugimoto, Y. Watanabe, N. Ozaki, A. Mizutani, Y. Takata, Y. Kitagawa, H. Ishikawa, N. Ikeda, K. Awazu, X. Wang, A. Watanabe, S. Nakamura, S. Ohkouchi, K. Inoue, M. Kristensen, O. Sigmund, P. I. Borel and R. Baets, "Photonic crystal and quantum dot technologies for all-optical switch and logic device," New J. Phys. 8, 208 (2006).
[CrossRef]

Y. A. Vlasov and S. J. McNab, "Coupling into the slow light mode in slab-type photonic crystal waveguides," Opt. Lett. 31, 50-52 (2006).
[CrossRef] [PubMed]

L. H. Frandsen, A. V. Lavrinenko, J. Fage-Pedersen, and P. I. Borel, "Photonic crystal waveguides with semi-slow light and tailored dispersion properties," Opt. Express 14, 9444-9450 (2006).
[CrossRef] [PubMed]

2005 (1)

2004 (5)

2002 (2)

S. G. Johnson, P. Bienstman, M. A. Skorobogatiy, M. Ibanescu, E. Lidorikis, and J. D. Joannopoulos, "Adiabatic theorem and continuous coupled-mode theory for efficient taper transitions in photonic crystals," Phys. Rev. E 66, 066608 (2002).
[CrossRef]

Y. Sugimoto, N. Ikeda, N. Carlsson, K. Asakawa, N. Kawai and K. Inoue, "Fabrication and characterization of different types of two-dimensional AlGaAs photonic crystal slab," J. Appl. Phys. 91, 922-929 (2002).
[CrossRef]

2001 (1)

M. Notomi, K. Yamada, A. Shinya, J. Takahashi, C. Takahashi, and I. Yokohama, "Extremely large group-velocity dispersion of line-defect waveguides in Photonic Crystal Slabs," Phys. Rev. Lett. 87, 253902 (2001).
[CrossRef] [PubMed]

1988 (1)

Appl. Phys. Lett. (1)

A. Yu. Petrov and M. Eich, "Zero dispersion at small group velocities in photonic crystal waveguides," Appl. Phys. Lett. 85, 4866-4868 (2004).
[CrossRef]

Electron. Lett. (1)

Y. Tanaka, Y. Sugimoto, N. Ikeda, H. Nakamura, K. Asakawa, K. Inoue, and S. G. Johnson, "Group velocity dependence of propagation losses in single-line-defect photonic crystal waveguides on GaAs membranes," Electron. Lett. 40, 174-176 (2004).
[CrossRef]

J. Appl. Phys. (1)

Y. Sugimoto, N. Ikeda, N. Carlsson, K. Asakawa, N. Kawai and K. Inoue, "Fabrication and characterization of different types of two-dimensional AlGaAs photonic crystal slab," J. Appl. Phys. 91, 922-929 (2002).
[CrossRef]

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

New J. Phys. (1)

K. Asakawa, Y. Sugimoto, Y. Watanabe, N. Ozaki, A. Mizutani, Y. Takata, Y. Kitagawa, H. Ishikawa, N. Ikeda, K. Awazu, X. Wang, A. Watanabe, S. Nakamura, S. Ohkouchi, K. Inoue, M. Kristensen, O. Sigmund, P. I. Borel and R. Baets, "Photonic crystal and quantum dot technologies for all-optical switch and logic device," New J. Phys. 8, 208 (2006).
[CrossRef]

Opt. Express (3)

Opt. Lett. (2)

Phys. Rev. E (1)

S. G. Johnson, P. Bienstman, M. A. Skorobogatiy, M. Ibanescu, E. Lidorikis, and J. D. Joannopoulos, "Adiabatic theorem and continuous coupled-mode theory for efficient taper transitions in photonic crystals," Phys. Rev. E 66, 066608 (2002).
[CrossRef]

Phys. Rev. Lett. (1)

M. Notomi, K. Yamada, A. Shinya, J. Takahashi, C. Takahashi, and I. Yokohama, "Extremely large group-velocity dispersion of line-defect waveguides in Photonic Crystal Slabs," Phys. Rev. Lett. 87, 253902 (2001).
[CrossRef] [PubMed]

Other (2)

H. Nakamura, K. Kanamoto, Y. Sugimoto, N. Ikeda, Y. Tanaka, Y. Nakamura, S. Ohkouchi, and K. Asakawa, "High-efficiency coupling to photonic crystal waveguide with low group velocity by hetero photonic crystal technique," presented at the Fifth Int. Symp. Photonic and Electromagnetic Crystal Structures (PECS-V), Kyoto, Japan, 7-11 March 2004.

K. Inoue, in Photonic Crystals, K. Inoue and K. Ohtaka, eds., (Springer-Verlag, Berlin Heidelberg, 2004).

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Figures (10)

Fig. 1.
Fig. 1.

Schematic explaining the Hetero-Vg PC waveguide. (a) Recovery of the transmittance of slow light pulse by the Low-Vg region between High-Vg regions. The reflectance at the boundary of the WG, due to the group index (ng ) difference, should be suppressed. (b) Variation in the transmittance and ng as a function of wavelength. The transmittance decreases and ng increases with the wavelength approaching the band-gap. The transmittance has been recovered using the Ht-Vg WG.

Fig. 2.
Fig. 2.

(Upper) Model of the Ht-Vg WG for 2D calculations. (Lower) The band structure of each region for TE mode, where the solid black line indicates the light line. The corresponding wavelength is calculated to have the Vg, 0.17c at H-Vg regions and 0.05c at the L-Vg region, where c is the velocity of light in a vacuum.

Fig. 3.
Fig. 3.

Comparison of the propagating pulse light intensity as a function of time between the detectors along the Hetero-Vg WG and Homo-L-Vg WG.

Fig. 4.
Fig. 4.

SEM plan-view images of the fabricated sample.

Fig. 5.
Fig. 5.

Experimental setup for measuring the group velocity (Vg) of a light pulse propagating in the PC-WG via the time-of-flight interference method.

Fig. 6.
Fig. 6.

The observed transmittance spectra of CW white-light through H-Vg, L-Vg and the L=36μm and 144 μm Ht-Vg WGs.

Fig. 7.
Fig. 7.

(a) Observed interference signals of the pulse propagating in the Homo-Vg WG of various wavelengths. (b) Plots of transmittance and ng as a function of wavelength.

Fig. 8.
Fig. 8.

The observed interference signals of the pulse at various wavelengths propagating through the Ht-Vg WG having the 36-μm-length L-Vg region.

Fig. 9.
Fig. 9.

(a) Plot of delay times as a function of L-Vg region length for the Ht-Vg WGs at various wavelengths. (b) The deduced Vg and ng in the L-Vg region of the Ht-Vg WG for various wavelengths.

Fig. 10.
Fig. 10.

Summary of transmittance and ng of the pulse through the Ht-Vg and Homo-Vg WGs as a function of wavelength. In the transmittance of the Ht-Vg WG (L=36μm), 16dB recovery including 12dB coupling improvement at ng =17 compared to the Homo-Vg WG was confirmed.

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