Infrared Metamaterials for Diffractive Optics

Infrared Metamaterials for Diffractive Optics by Yu-Ju Tsai Department of Electrical and Computer Engineering Duke University Date:___________________________ Approved: ___________________________ David R. Smith, Advisor ___________________________ Nan M. Jokerst ___________________________ Jungsang Kim ___________________________ Adrienne D. Stiff-Roberts ___________________________ Joseph A. Izatt An abstract of a dissertation submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy in the Department of Electrical and Computer Engineering in the Graduate School of Duke University 2013 Copyright by Yu-Ju Tsai 2013 iv Abstract Intense developments in optical metamaterials have led to a renaissance in several optics fields. Metamaterials, artificially structured media, provide several additional degrees of freedom that cannot be accessed with conventional materials. For example, metamaterials offer a convenient and precise way to explore a wide range of refractive indices, including negative values. In this dissertation, I introduce the idea of metamaterial based diffractive optics. Merging diffractive optics with metamaterials has several benefits, including access to almost continuous phase profiles and a wide range of available controlled anisotropy. I demonstrate this concept with several examples. I begin with an example of metamaterial based blazed diffraction grating using gradient index metamaterials for λ = 10.6 μm. A series of non-resonant metamaterial elements were designed and fabricated to mimic a saw-tooth refractive index profile with a linear index variation of 3.0 n ∆ = . The linear gradient profile is repeated periodically to form the equivalent of a blazed grating, with the gradient occurring across a spatial distance of 61 μm. The index gradient is confirmed by comparing the measured magnitudes of the -1, 0 and +1 diffracted orders to those obtained from full wave simulations.