Nano-mechanics of Optical Structures for High Laser-Damage Threshold Applications

Karan Mehrotra, Ph.D. Defense

Hopeman 224

Nano-structured optical materials such as amorphous silica diffraction gratings on multilayer dielectric (MLD) thin films are critical components and performance enhancers in high-power laser applications such as in inertial confinement fusion experiments. We use nano-indentation, electron microscopy and finite-element (2D and 3D) simulations to measure and observe the nano-mechanical material properties (elastic, plastic, and fracture) of nm-level features along with their associated defects in important optical components that include single layer and multi-layer oxide films, and optical diffraction gratings. Our work reveals that elasticity, ductility and fracture at the nm-level can be studied separately, in contrast to micromechanical deformation; that SEM plays an important role in identifying relevant features; that in addition to characterization, nanoindentation may be useful as a diagnostic tool; and that numerical simulations naturally complement the experimental nano-mechanics to model the complex nm-level response of optical nanostructures.