Non-linear optical effects in cold and hot rubidium gases

Abstract

The front cover shows a microscope image of a bridge waveguide, with tapered launchpads at each side. The launchpads contain the surface grating couplers designed in chapter 2 of this thesis. The freestanding, 200 nm wide and 100 µm long bridge was fabricated using e-beam lithography in a 220 nm thin silicon nitride membrane by Andries Lof at the Amolf Nanolab Amsterdam. The image is taken in the Fourier microscope setup shown in figure 2.5, with white light illumination using an LED. The back cover shows an image of the same bridge waveguide, which is mirrored to represent the bottom view of the sample. It is best viewed by holding the thesis face up and lifting it over your head to investigate the 'sample' from underneath. For this image, the bottom launchpad is illuminated with laserlight with a wavelength of 780 nm under an angle of 3 • from normal incidence. The light is coupled into the membrane and funneled into the waveguide bridge. A bright spot is visible at the waveguide bridge entrance due to enhanced scattering. The light then travels through the bridge and is coupled out at the top launchpad. The image demonstrates that light can be coupled into the nanophotonic waveguide bridge using surface grating couplers under near-normal incidence.