Exploring negative refraction conditions for quantum cascade semiconductor metamaterials in the terahertz spectral range

Abstract

In order to avoid losses in metamaterial unit cells at frequencies of interest, caused by metallic inclusions, an active medium design has been proposed. As candidate structures for this active medium, we have chosen quantum cascade lasers because of their high output gain. Here we analyze and compare two quantum cascade structures that emit at 4.6 THz and 3.9 THz, respectively, placed under the influence of a strong magnetic field. We first solve the full system of rate equations for all relevant Landau levels, and obtain the necessary information about carrier distribution among the levels, after which we are able to evaluate the permittivity component along the growth direction of the structure. With these data one can determine the conditions under which negative refraction occurs, and calculate the values of the refractive index of the structure, as well as the range of frequencies at which the structure exhibits negative refraction for a predefined total electron sheet density.

Tailoring mode interference in plasmon-induced transparency metamaterials

“…Metamaterials, made of well-ordered artificial metal or dielectric subwavelength unit cells, are the most pivotal example in light manipulation. Metamaterials can be engineered to realize nearly arbitrary values of effective electromagnetic parameters, boosting the development of exotic electromagnetic properties that are inaccessible in natural materials, such as zero refractive index [1,2], negative refractive index [3,4], ultra-high refractive index [5], hyperbolic [6,7], chiral manipulation [8,9], as well as filtering [10,11], perfect absorption [12][13][14][15], polarization control [16][17][18], sensing [19], waveguiding [20] and nonlinearity enhancement [21]. The ever-increasing demands for terahertz (THz) devices greatly promote studies on THz metamaterials and lead to revolutions in THz generation, modulation and detection.…”