title: Composite acoustic medium with simultaneously negative density and modulus.
abstract: We fabricated an acoustic composite structure consisting of a periodic array of interspaced membranes and side holes. Experimental data on the transmission, effective density, and phase velocity are presented. The system exhibits two critical frequencies, omega{SH} and omega{c}. Our metamaterial is double negative and transparent for frequencies lower than omega{SH}. For the frequencies omega{SH}<omega<omega{c}, the medium is opaque and only the density is negative. For the frequencies above omega{c}, the system is double positive and transparent. The present medium exhibits a very wide double negative spectral range that opens the possibility of the application of metamaterials for "white lights."
authors.affiliation: Institute of Physics and Applied Physics, Yonsei University, Seoul 120-749, Korea.
authors.forename: Sam Hyeon
authors.initials: SH
authors.lastname: Lee
authors.forename: Choon Mahn
authors.initials: CM
authors.lastname: Park
authors.forename: Yong Mun
authors.initials: YM
authors.lastname: Seo
authors.forename: Zhi Guo
authors.initials: ZG
authors.lastname: Wang
authors.forename: Chul Koo
authors.initials: CK
authors.lastname: Kim