Laser processing of plasmonic metal oxides and phase change materials

Plasmonic materials have attracted great attention due to their ability to enhance light-matter interactions. Noble metals such as Au and Ag have been well studied as materials for plasmonic devices. However, these metals are not suitable for mid infrared (IR) plasmonic applications due to their relatively large optical losses, which are detrimental to device efficiency. Metal oxides, on the other hand, have been proposed for low loss metallic components in the mid IR because they can provide a tunable carrier density by varying the concentration of dopants or defects (oxygen vacancies). The epsilon-near zero wavelength of the real part of the dielectric permittivity of these metal oxides, for example, can easily be tuned from 1.5 mu m to 4 mu m by adjusting doping or defect levels. Optical losses in devices made from these metal oxide materials generally exhibit lower losses than those obtained with conventional metals. We have investigated laser processing techniques for synthesizing several types of metal oxides such as indium tin oxide and phase change materials such as VO2. First, pulsed laser deposition was used to grow these oxide thin films. Second, an ultrafast laser was used to spatially pattern the thin films via a direct laser interference patterning (DLIP) configuration while simultaneously producing laser induced periodic surface structures (LIPSS) resulting in a uniaxial surface morphology. We will present details of the laser processing conditions on surface morphology, electrical, and optical properties of these laser processed metal oxide films.