Strongly anisotropic media: the THz perspectives of left-handed materials

The materials with negative refractive index [1] (also known as left-handed media, LHM) have attracted a great deal of attention during recent years [2, 3, 4, 5, 6, 7, 8, 9, 10, 11]. However, despite numerous efforts to bring LHMs to optical or even THz domain [12, 13, 14], all modern realizations of these fascinating systems are limited to GHz waveguides[7, 9, 15, 16]. LHMs associated with materials with simultaneously negative values of dielectric constant ǫ and magnetic permeability μ, are typically based on several interconnected resonant structures. A fraction of these resonators is used to achieve negative dipole response, while others provide negative magnetic response [7, 16]. This basic LHM design however immediately leads to two problems. First, high-Q resonators needed in this approach, require extreme fabrication accuracy and uniformity across the the system – something which is currently unachievable on a massproduction scale. Furthermore, the operation in a proximity of any resonance is typically accompanied by strong resonant absorption – with the resulting loss of resolution [17]. An alternative approach of using photonic crystals to achieve a negative phase velocity [8], besides being sensitive to minute defects in the actual fabricated structure, typically yields direction-dispersive index of refraction with corresponding deterioration of optical properties. A new approach to obtain a left-handed response has been recently proposed in Ref. [18]. In contrast to the resonantbased systems described above, the proposed material is non-magnetic (i.e. μ ≡ 1), with the negative-n response achieved in a waveguide configuration with anisotropic dielectric core. In this work we study the imaging properties of these non-magnetic LHMs, and propose their THz realization based on a homogeneous, naturally occurring material.