Acoustic modulation of photonic crystal waveguides

Contacts:

Mike van der Poel, DTU Fotonik, 4525 3660 (mvdp@fotonik.dtu.dk)

Elaine C.S. Barretto, DTU Fotonik, 4525 6373 (ecsb@fotonik.dtu.dk)

Scanning surface electron micrograph (SEM) of a photonic crystal waveguide (right) and a SAW-generating transducer (left). The inset in the upper right shows an enlargement of the PhC WG. The light is guided along the path of filled holes. The hole size is 250 nm and the lattice constant (i.e. hole-to-hole spacing) is 380 nm in this sample.

Photonic crystal waveguides (PhC WGs) as shown in the illustration have become very popular as one of the main building blocks in modern nanophotonics components. There are several good reasons for this: One is that it is possible to engineer the dispersion properties so that the light is slowed down, another is that it is possible to confine the light tightly and bend it around very sharp corners.

At DTU Fotonik, we are working with the modulation of PhC WGs by surface acoustic waves (SAWs). The SAW is like a nano-earthquake that changes the refractive index of the PhC and therefore changes its light guiding properties. This can lead to many interesting optical components such as light frequency shifters, switches and more. In this project you will mainly work with theoretical simulation of the light wave as it propagates through the SAW modulated PhC. But the project will also give you a chance to do experimental characterization of actual devices. For the modelling part you will learn to use programs such as COMSOL, Crystal Wave, and MatLab. You will work on understanding the physics behind the wave propagation and perform realistic numerical simulations of components that can be manufactured at the DTU clean room DANCHIP or at other facilities.