Design and Characterization of Silicon Waveguide Cavities

Placing quantum materials into optical cavities promises active control of material properties and functionality. Low-dimensional systems are particularly susceptible and exhibit electronic phases that can be switched by an external stimulus. However, the required extreme light-matter coupling is hampered by intrinsic cavity losses. Here, we work towards the integration of a prototypic Peierls insulator at the surface of a silicon waveguide resonator. This project focuses on the creation of the resonator. A resonator couples the light into the sample by always totally internally reflecting it, thus generating the evanescent fields used in light matter coupling. To couple the light into the wafer, the angle of reflection has to be controllable. To do this, we used diffraction gratings etched onto the surface with varying periods. Next, we used Fabry-Pérot interference to maximize the effect of the evanescent fields. As a result, the resonance conditions of a 25 µm thick wafer were observed and accurately predicted for the first four resonance peaks. The two aspects of this project will be combined in future, with etched diffraction gratings on a thin wafer. The longer term steps are test platforms like silicon membranes and e-beam etched wafers.