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 subwavelength-scale 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.
Wounjhang Park, Guest Editor for this issue of MRS Bulletin, can be reached at the University of Colorado, Department of Electrical and Computer Engineering, Campus Box 425, Boulder, CO 80309-0425, USA; tel. 303-735-3601, fax 303-492-2758, and e-mail email@example.com.
Park is an associate professor of Electrical and Computer Engineering at the University of Colorado at Boulder. He received his PhD degree from the Georgia Institute of Technology and subsequently worked at the Georgia Tech Research Institute as a research faculty member. Park has been with the University of Colorado at Boulder since 2001. His research interests include nanophotonics, biophotonics, and flat panel displays. Park also is a Ruth L. Kirschstein NRSA Senior Fellow in Cancer Nanotechnology Research and an editorial board member of the Journal of Computational and Theoretical Nanoscience.
Jinsang Kim, Guest Editor for this issue of MRS Bulletin, can be reached at the Materials Science and Engineering Department, 2098 H.H. Dow Bldg., 2300 Hayward St., Ann Arbor, MI 48109-2136, USA; tel. 734-936-4681, fax 734-763-4788, Web sites msewww.engin.umich.edu/people/fac-ulty/kim and www.engin.umich.edu/dept/cheme/people/kim.html.
Kim is an assistant professor with joint appointments in the Departments of Materials Science and Engineering, Chemical Engineering, Biomedical Engineering, and Macromolecular Science and Engineering at the University of Michigan, Ann Arbor. He holds MS and BS degrees from Seoul National University, Korea, both in fiber and polymer science. Kim earned his PhD degree in materials science and engineering from the Massachusetts Institute of Technology in 2001, under the supervision of Timothy Swager. During this time, he studied the design, synthesis, and assembly of conjugated sensory polymers and energy transport properties in controlled structures. Kim's postdoctoral work in the laboratory of David Tirrell at the California Institute of Technology involved the expression of artificial genes to determine the extent to which artificial genetic information can be used to encode supramolecular assembly in macromolecular systems. Since 2003, Kim's research interests at the University of Michigan have included self-signal amplifying biosensors and sensor arrays, flexible solar cells, highly emissive organic emitters, and negative index materials sponsored by the National Science Foundation, the Air Force Office of Scientific Research, the American Chemical Society (ACS), the Korea Institute of Machinery and Materials, and the Center for Chemical Genomics. In addition, he is the recipient of several prestigious awards including the 2007 NSF CAREER Award, the 2006 Holt Award for excellent teaching, the 2002 International Union of Pure and Applied is Chemistry Prize for Young Chemists, the 2002 ACS ICI Award, and the 2000 MRS Graduate Student Gold Award.