Metamaterials are engineered materials which can produce effects otherwise unattainable with natural materials. Therefore, metamaterials can be used to manipulate energy fields in order to achieve specific and tailored functionalities. In this thesis, the design and performance of two-dimensional (2-D) metamaterials, called metasurfaces, for wavefront manipulation, are studied. Numerous engineering applications require the manipulation of the wavefront of an incoming beam. Examples of this manipulation include beam-steering or wavefront focusing. Traditionally, beam-steering is implemented using phased arrays (e.g., antenna arrays for electromagnetic waves, transducer arrays for sound waves), and beam focusing is implemented using lenses. The goal of this work is to achieve these functionalities (e.g., redirection, focusing) using metasurfaces. Several applications for beam manipulation are studied. The work presented in this dissertation is divided two application spaces: electromagnetic metamaterials and acoustic metamaterials.

In the electromagnetics space, the first application is in the terahertz (THz) spectrum. A tunable beam-steering method for THz radiation is studied and evaluated using a metasurface composed of THz antennas. Simulations are performed using finite element method HFSS for electromagnetic structures. The theoretical analysis is complemented by system integration and experimental demonstration. The second application is in the radio frequency range and involves reshaping the radiation emitted by an antenna with the purpose of improving its directivity. Modeling studies are performed using finite element methods (e.g., HFSS).

In the acoustics space, the focus is on the beam-steering of acoustic plane waves. The unit cell of an acoustic metamaterial for beam steering is described. The design strategy of the metamaterial plate for beam-steering is described. Tuning mechanisms for tunable beam-steering are introduced and described. Modeling is performed using the finite element analysis tool COMSOL.