Negative-Index Materials: Optics by Design
- PDF / 715,774 Bytes
- 8 Pages / 612 x 792 pts (letter) Page_size
- 64 Downloads / 240 Views
Materials: Optics by Design Wounjhang Park and Jinsang Kim, Guest Editors
Abstract Index of refraction, a fundamental optical constant that enters in the descriptions of almost all optical phenomena, has long been considered an intrinsic property of a material. However, the recent progress in negative-index material (NIM) research has shown that the utilization of deep-subwavelength-scale features can provide a means to engineer fundamental optical constants such as permittivity, permeability, impedance, and index of refraction. Armed with new nanofabrication techniques, researchers worldwide have developed and demonstrated a variety of NIMs. One implementation uses a combination of electric and magnetic resonators that simultaneously produce negative permittivity and permeability, and consequently negative refractive index. Others involve chirality, anisotropy, or Bragg resonance in periodic structures. NIM research is the beginning of new optical materials research in which the desired optical properties and functionalities are artificially generated. Clearly, creating negative index materials is not the only possibility, and the most recent developments explore new realms of materials with near-zero indexes and inhomogeneous index profiles that can produce novel phenomena such as invisibility. Furthermore, the concept of controlling macroscopic material properties with a composite structure containing subwavelengthscale features extends to the development of acoustic metamaterials. By providing a review of recent progress in NIM research, we hope to share the excitement of the field with the broader materials research community and also to spur new ideas and research directions.
Introduction
Index of refraction, or refractive index, is a fundamental constant describing the interaction between light and material. Index of refraction quantifies, for example, how fast light travels in a material and how strongly a material reflects light on its surface. Vacuum is the reference medium, with unity index of refraction. In a material, electrons and atoms interact with the electromagnetic field of light, giving rise to an index of refraction specific to the material. Although index of refraction is generally frequency-dependent, all naturally occurring materials are known to have indexes of refraction that are greater than 1. Is it possible to have a negative index of refraction? This question was pondered as early as 1904.1 No physical principle prohibits negative index of refraction. In 1968, Veselago theorized that a material
with negative permittivity and permeability should have a negative index of refraction and that such a material should exhibit a reverse Doppler effect, a reverse Cherenkov effect, and reversed focusing properties in lenses.2 Negative-index materials (NIMs), however, remained in the realm of purely theoretical imagination until Pendry’s seminal article3 in 2000 ignited major research activities worldwide. In that work, Pendry predicted the possibility of a superlens that could focus light to
Data Loading...
