The effect of dielectric metamaterials on ultrashort laser pulses

Sammanfattning

Dielectric metasurfaces are the state of the art of functional optical devices with light manipulating capabilities. Metasurfaces are planar devices which makes them highly efficient since they do not suffer from propagation effects. These devices consist of sub-wavelength dielectric structures arranged in a lattice, situated on a substrate of dielectric or metallic material. They have been shown to have the ability of local phase and polarization control. Furthermore, due to their design, they are a promising candidate to replace conventional refractive and diffractive optics as a more compact and versatile option. Their light manipulating capabilities stem from their sub-wavelengths structures which support Mie resonances. With these resonances, light can be locally confined in the metasurface, allowing for local control of light on a sub-wavelength scale. Many metasurfaces in research are considered for continuous wave sources, but in recent years, ultrafast physics has made advances with dielectric metasurfaces. As setups for pulse-shaping in ultrafast physics are large and suffer from losses, metasurfaces could be a functional alternative. In this thesis, the pulse-manipulating capabilities of dielectric metasurfaces are investigated. By solving Maxwell’s equations in the time domain, the response of dielectric metasurfaces are investigated when femtosecond pulses are incident on them. It was found that, by designing a metasurface that has resonances within the spectrum of the pulse, the metasurface exhibited pulse manipulating capabilities. Pulse-splitting, spectral filtering and temporal oscillations of the pulse envelope were found as properties of designed metasurfaces. This work defines a starting point for the design of dielectric metasurfaces for the manipulation of ultrashort laser pulses in the temporal and spectral domain.