The demands for ever increasing data speed in communication technology have inspired the idea of all optical integrated chips where the optical field plays a role similar to electrons in present-day electronics. Such all-optical chips will provide much higher data rates as well as lower power consumption, and a key component in such chips is the transistor. Its basic functionality is to control the amplification or absorption of an optical signal pulse by use of a control pulse, thus constituting the optical equivalent of electronic transistors. Unlike electrons, however, beams of light do not interact (the beams from two flashlights, for example, simply pass though each other). However, we can use non-linear effects, for instance in semiconductor quantum dots, to dynamically change material properties such as the refractive index, and in this way we can effectively control one pulse of light with another, as illustrated in the figure.

Project description: In this project we will set up a simple, yet powerful model for light propagation in a photonic crystal circuit and use it to model an all optical transistor. The model will be based on so-called temporal coupled mode theory and tested using finite-difference time-domain calculations. In this project you will: Learn about fundamental properties of optical integrated circuits including waveguides, cavities and non-linear materials. Develop a model of an optical circuit and use it to model non-linear switching in a photonic crystal based all optical transistor. Test the model by comparing to numerical finite-difference time-domain calculations.