Thursday, February 6, 2014
Mechanical and Civil Engineering Seminar
Dielectric Metamaterials Go Optical
Jason Valentine, Assistant Professor , Department of Mechanical Engineering, Vanderbilt
Electromagnetic metamaterials are artificially structured materials wherein artificial atoms are utilized to engineer the optical properties of the composite, opening the door to optical properties not present in naturally occurring materials. Traditionally, metamaterials are formed from structured metals, however, as these materials are scaled to high frequencies they become increasingly absorptive due to Ohmic damping. This absorption loss continues to be one of the primary impediments to their application at infrared and visible frequencies. Dielectric metamaterials offer one potential solution to this issue by eliminating Ohmic loss, allowing highly transparent metamaterials while also preserving the freedom to freely engineer the optical properties. In this talk, I will discuss our recent efforts to develop purely dielectric metamaterials which exhibit low absorption loss at optical frequencies. These metamaterials are formed from semiconductor based unit cells that exhibit both electric and magnetic Mie resonances, allowing us to manipulate the optical properties of the composite. I will outline the implementation of both 2D and 3D metamaterial designs. I will discuss how 2D metamaterials, or metasurfaces, can be used to tailor the wavefront of light at a surface for applications such as lensing, complex beam formation, and polarization control. I will also discuss how we have used 3D dielectric metamaterials for achieving an impedance matched near-zero refractive index at optical frequencies. Such materials can be applied for a variety of applications including directional emitters, low threshold lasers, and boosting the efficiency of non-linear conversion processes.