OP: A new THz technology: artificial dielectrics

Brown University, Providence RI

Investigators

Abstract

Terahertz waves, spanning frequencies ranging from about 0.1 THz to about 5 THz (wavelengths from 3 mm to 0.06 mm), are ideal for a wide variety of applications in communications, homeland security, medical diagnosis, non-destructive evaluation, quality control, and environmental monitoring. In fact, the terahertz field has become one of the most exciting research frontiers in recent years, stimulating a great deal of interest even in the popular culture. The above potential benefits to society have fueled the need for more versatile and energy efficient technologies to control and manipulate terahertz waves, compared to what is currently available. Therefore, this research aims to develop a new terahertz technology based on what are known as artificial dielectrics. Artificial dielectrics are man-made media that mimic the properties of naturally occurring dielectric media, or even manifest properties that cannot generally occur in nature. For example, the well-known dielectric property, the refractive index, which usually has a value greater than unity, can have a value less than unity in an artificial dielectric. This new technology will be analogous to the emerging technology of metamaterials that is revolutionizing the field of optics. Metamaterials are also man-made media that can control the flow of light even in counter-intuitive ways. In fact, the proposed technology offers many of the same intriguing possibilities as that of metamaterials. A key advantage of the technology is the ability to engineer the refractive index continuously, thereby being able to realize inhomogeneous media. In contrast, continuous variation of the electromagnetic properties is more challenging to achieve in metamaterials. Therefore, if one considers the impact metamaterials has had on the field of optics, the proposed research is bound to have an enormous impact in advancing the field of terahertz-wave sciences. This proposal will also promote educational outreach in terms of training and educating graduate, undergraduate, and pre-college students. This artificial dielectric concept provides an intriguing engineering platform to introduce budding scientists to fundamental physical phenomena. The primary goal of this research program is to develop a new technology for the control and manipulation of terahertz waves utilizing artificial dielectrics. During the course of this project, several key terahertz-wave devices will be developed via this new technology. These artificial- dielectric devices will have far better performance than existing similar functional devices, and will enable capabilities that are currently not available in the terahertz-wave regime. The scope of the research can be divided into two main thrusts. In one thrust, devices will be developed utilizing the homogenous version of the artificial dielectric. These devices will include wave- plates and polarizing beam-splitters. In the other thrust, devices will be developed utilizing the inhomogeneous version of the artificial dielectric. These will include gradient-index (GRIN) devices, such as the Maxwell' fish-eye lens and the Luneburg lens. The experimental work will be carried out using time-domain terahertz systems that are capable of generating and detecting picosecond pulses comprising of a baseband terahertz spectrum. In these systems, the transmitter and receiver modules are fiber coupled to provide the necessary degrees of freedom since beam paths are not always in line-of-sight. Importantly, this artificial-dielectric technology will resolve the long-standing problem of realizing high-index gradients, which has hampered the practical use of powerful GRIN devices. This work will also shed more light into the predicted super-resolution (perfect imaging that is not limited by the wavelength) phenomenon associated with the Maxwell' fish-eye lens. These research developments will have an enormous impact on the terahertz field by providing many new components and capabilities for the control and manipulation of terahertz waves.