Photon Management on a Photonic Crystal Platform

Abstract

A multilayered dielectric structure, namely a one dimensional photonic crystal (1DPC), is proposed as a suitable platform for photon management, due to the low absorption of the dielectric materials. When properly designed, a 1DPC can sustain surface electromagnetic modes called Bloch Surface Waves (BSWs). In this PhD Thesis it is shown how light coupled to BSW can be focused or guided by means of ultrathin polymeric refractive structures directly patterned on the surface. Moreover, by patterning the surface with surface relief gratings, far-field radiation can be efficiently coupled to the surface modes, thus providing an enhanced electromagnetic field at the truncation interface of the 1DPC. By shaping the grating in a circular symmetry, light can be in-plane focused into a sub-wavelength spot. The same structure can be used to re-shape the radiation pattern of dipolar emitters. It is shown that an emitter lying on the surface of the 1DPC couples to the photonic structure and the fluorescence radiated couple with the surface modes. The so called BSW-coupled fluorescence propagates along the surface with low losses and a well-defined wavevector. By means of surface diffraction gratings properly designed, fluorescence can be extracted along any direction, thus improving the fluorescence collection with no need of high numerical aperture optics or critical alignements. A novel method for evaluating the enhancement gained with such photonic structures on the extraction efficiency is proposed. Such method is capable of providing at the same time spatial resolution, angular resolution and spectral resolution. A biosensing experiment to detect small amounts of labeled proteins is provided, in order to show the sensing capabilities of the photonic structure