Negative Refraction in Photonic Crystals Zhi-Yuan Li, Lin Gan, Zhi-Fang Feng, Kun Ren, Shuai Feng, and Dao-Zhong Zhang

Laboratory of Optical Physics, Institute of Physics, Chinese Academy of Sciences, P. O. Box 603, Beijing 100080, China

Tel: 86-10-82648106; Fax: 86-10-82649356; Email: lizy@aphy.iphy.ac.cn

We report our recent works on negative refraction in 2D and 3D photonic crystals. The major point is to design and realize photonic crystal structures with high-performance negative refraction and imaging properties from theoretical and experimental sides.

The first aspect of our work concerns design and realization of non-near-field negative-refraction imaging [1]. Several ways were found to this end. One is to use 12-fold quasicrystal structure which shows an effective index of refraction close to -1 in a wide range of light propagation direction [2,3]. The other is to use a deliberately designed metallo-dielectric photonic crystal where the effective index of refraction is -1 in almost any propagation direction of light [4]. Non-near-field focusing and imaging behavior is realized in such a structure and the object and image distance satisfies the conventional Gaussian law of lens excellently.

The second aspect of our work is to realize tunable negative refraction properties. Several ways were examined to tune the intrinsic band diagrams and equifrequency surface configurations of photonic crystals. One is to use low-symmetry building block, such as elliptical or rectangular rods in 2D photonic crystal, and controlling their orientation [5,6]. Another is to change the refractive index of background medium in a metal-cylinder photonic crystal [7]. The other is to use electro-optical materials as the building block and impose external electric or magnetic fields to change the refractive index contrast [8].

The third aspect of our work is to realize negative refraction in the optical wavelengths. To this end we consider photonic crystal structures that are of sub-micrometer feature scale and allow relative ease of fabrication by state-of-the-art technologies, such as self-assembly technique and microfabrication technique for a. We have found that 3D inverse-opal silicon photonic crystals, a structure that can be readily synthesized via self-assembly and template casting techniques in the infrared and visible size regimes, can exhibit 3D negative refraction and focusing properties at the (111) growth direction [9]. More recently, we have designed structures based on 2D silicon photonic crystal slab that exhibit negative refraction around 1.55um. Optical measurements via scanning near-field optical microscopy disclose clear pictures of high-performance negative refraction of incident infrared beam by the structure. We believe that the experimental efforts on optical negative refraction structures should help to encourage more strength input on realizing negative refraction, superlensing, superprism, and other dispersion control properties in optical photonic crystals and other metamaterials and exploring unknown realms. References: 1. Z. Y. Li and L. L. Lin, Phys. Rev. B 68, 245110 (2003). 2. Z. Feng , X. Zhang, Y. Wang, Z.Y. Li, B.Y. Cheng, and D. Z. Zhang, Phys. Rev. Lett. 94, 247402 (2005). 3. X. Zhang, Z. Y. Li, B. Y. Cheng, and D. Z. Zhang, Optics Express 15, 1292 (2007). 4. Z. F. Feng, X. Zhang, K. Ren, S. Feng, Z. Y. Li, B. Y. Cheng, and D. Z. Zhang, Phys. Rev. B 73，075118 (2006). 5. S. Feng, Z.Y. Li, Z. F. Feng, B. Y. Cheng, and D. Z. Zhang, Phys. Rev. B 72, 075101 (2005).

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6. S. Feng, Z.Y. Li, Z. F. Feng, B. Y. Cheng, and D. Z. Zhang, J. Appl. Phys. 98, 063102 (2005). 7. S. Feng, Z.Y. Li, Z. F. Feng, B. Y. Cheng, and D. Z. Zhang, Appl. Phys. Lett. 88, 031104 (2006). 8. K. Ren, Z. Y. Li, X. B. Ren, B. Y. Cheng, and D. Z. Zhang, Appl. Phys. A 87, 181 (2007). 9. K. Ren, Z. Y. Li, X. B. Ren, S. Feng, B. Y. Cheng, and D. Z. Zhang, Phys. Rev. B 75, 115108 (2007).