Summary: Integrated Optical Micro Systems
Individual Research Project (IOO)
Design of photonic crystal cavity for effective optical
Photonic crystals can be formed by introducing a periodic index contrast in one, two or three
dimensions. A photonic bandgap (PBG) can exist analogous to the electronic bandgap in
semiconductor materials. The index contrast determines the size of the PBG. For silicon-air
structures, the periodicity is typically about 1/3 of the wavelength in vacuum, resulting in sub-
micrometer structures for operation in the infrared. Local defects with the size of one or a few
periods can act for example as resonators, filters or waveguides. This property makes
photonic crystals a viable candidate for densely integrated photonic structures.
A switching of optical signal between waveguides can be realized with a very compact device
by exploiting the properties of photonic crystal. A cavity in a photonic crystal can used to
selectively couple certain wavelength from waveguide to another. However, typically a
resonating mode of the cavity couples its energy to all 4 ports equally.
The task is to design a photonic crystal cavity that supports so-called degenerate modes
and makes effective switching in a 4-port photonic crystal device effective.