Dynamic tuning of photonic crystal nanocavities

Photonic crystal nanocavities play an important part in the future of nanophotonics. For many systems containing nanocavities it is necessary to be able to tune their essential parameters. In this thesis experimental investigation and control of properties of single and coupled photonic crystal nanocavities are presented. Experiments are supported by analytical and numerical calculations. An apparatus was built to probe nanophotonic samples over a wide wavelength range of IR light. Local control of nanostructures was achieved thermally by local laser heating with several pump lasers, where one of them can be shaped by a spatial light modulator. External laser wavelength reference scheme is developed, which allows to perform measurements with high speed and resolution. The local laser induced thermal tuning was found to greatly depend on the material of the nanostructure as well as on the ambient medium around the sample. We discovered that changing the ambient media from nitrogen to helium produces a change in the width of the temperature distribution by 30%, which easily allows an increase of the integration density of cavities on a nanophotonic chip. We managed to control several coupled nanocavities independently in the presence of thermal crosstalk. As a result, we annulled the disorder and restored the intended state of the system. To show the full tunability we successfully tuned the coupling constant between nanocavities experimentally using two proposed methods. In one method we directly thermally perturb the membrane between two directly coupled nanocavities, while in another one we use ancillary cavity to control the coupling. All post-pump time-dependent and permanent effects observed in experiments are summarized. While for some applications these changes are unwanted, for other ones they may be favorable, for example, permanent frequency shift may be applied to compensate disorder. Finally, the value of the linear thermo-optical coefficient of GaInP for a freely expanding material is measured using an isolated nanocavity resonance. The results described in this thesis extend boundaries of what can be achieved in nanophotonic circuits based on coupled nanocavities.