GaN- and VO 2-based nanostructures: physics and photonic applications

Abstract

This thesis presents fundamental research on potential materials and concepts for active photonic elements operating in the telecom wavelength regime. It is analyzed how the characteristics of the investigated nanostructures and the implementation of the proposed concepts could be applied in photonic research or devices. The first part of the thesis is devoted to the investigation of semiconductor heterostructures. The inter-miniband (IMB) transition in superlattices made of GaN and AlN in the cubic phase is characterized in terms of its linear and ultrafast nonlinear optical properties. In particular, the central energy and energetic width of the IMB transition is analyzed, and the time-scales of the electron relaxation are examined. In the second part, photonic and plasmonic applications of nanocrystals made of the phase change material vanadium dioxide (VO 2) are studied. It is shown how the optically-induced metal-insulator phase transition (MIT) can be utilized for the creation of reconfigurable active photonic elements. Different approaches to define diffraction gratings and Fresnel zone plates are presented. VO 2 based nanocomposites and the MIT are moreover utilized for research on surface plasmon polaritons (SPPs). Novel routes for the creation of plasmonic elements that allow for an active control of the light-SPP coupling strength are demonstrated. The concepts are based on the grating-assisted light-SPP coupling and the Kretschmann configuration.