The left-handed materials (LHMs) compose of two parts: magnetic component providing a negative magnetic permeability, and electric component yielding a negative electric permittivity. The composed-metamaterial (CMM) structures were designed, built, and measured in the microwave and the terahertz frequency ranges. In addition to the static MMs, tunable ones, which contain thermally, optically and electronically active materials, are also investigated.
Perfect absorption, using MMs, of electromagnetic (EM) waves is a budding research field for the potential applications in bolometer, sensor, etc. By minimizing the reflectance and eliminating the transmittance, the design and the fabrication of perfect absorbers (PAs) with near-unity absorption could be realized at microwave and terahertz bands.
For example, we proposed PA MMs based on flower-shaped structures, mimicking the photosynthesis by plants. The narrow peak of PA was obtained with an absorption of nearly 100% in both simulation and measurement. The frequency of PA peak was controlled by the size of flowers, and the symmetric geometry of this structure was utilized to achieve successfully the polarization independence.
The problem of EM noise comes to be more serious according to the advent of ubiquitous society, but the entry to the market for EM-wave materials is limited in absence of the essential technology. Extended dissemination of high-speed and high-f digital products and smart equipments has made special EM-wave materials used in various fields. We are also investigating advanced meta-structures and MMs for EM-wave absorption, aiming at these issues : MM technology for EM-wave absorption over 99% in a broad band, and MMs for EM-wave absorption independent of incident angle and polarization.
A relevant higher-level application can be advanced sensors for EM waves based on MM absorption, which might be applicable to a broad area in demand of sensing technology of EM wave, from thermal-image cameras using bolometers to near-ID detectors.
Other application fields of MMs are also mentioned, and challenging points for MMs are discussed to think about the improvements together. Future of the recent discovery of natural MM is forecasted, and perspective of MM researches is suggested.