Negative refractive index metamaterial with high transmission, low reflection, and low loss in the terahertz waveband.

The refractive index is a basic parameter of materials which it is essential to know for the manipulation of electromagnetic waves. However, there are no naturally occurring materials with negative refractive indices, and high-performance materials with negative refractive indices and low losses are demanded in the terahertz waveband. In this paper, measurements by terahertz time-domain spectroscopy (THz-TDS) demonstrate a metamaterial with a negative refractive index n of -4.2 + j0.17, high transmitted power of 81.5%, low reflected power of 4.3%, and a high figure of merit (FOM = |Re(n)/Im(n)|) of 24.2 at 0.42 THz. The terahertz metamaterial with these unprecedented properties can provide various attractive terahertz applications such as superlenses with resolutions beyond the diffraction limit in terahertz continuous wave imaging.