Photonic crystals

Two-dimensional photonic crystal slabs.

Photonic crystals involve a periodic lattice of two constituent materials which create a bandgap for light which forbids propagation for the relevant frequencies. They are the proven mechanism of controlling and manipulating light over small distances. Defects introduced in the lattice lift the bandgap at small, local regions thus allowing propagation, leading to formation of devices such as waveguides and resonators, that guide light, bend it sharply, or store it in small regions.

Intensity distribution in the line defect resonator.

Our object of interest is the line defect heterostructure resonator, which confines light on the virtue of waveguide-mode gaps, unlike conventional resonators that rely on photonic band gaps. We have studied field distributions of such resonators, and furthermore, we have observed a shift in the resonant frequency of the resonator when it interacts in the near-field with an NSOM tip.

Tunability range as a function of tip-sample distance, for various parameters.

The architecture of the line defect resonator offers a few physical parameters that can be tuned to actively control the resonant frequency of the resonator in real-time using the NSOM tip. We have recently numerically analyzed this shift by varying the parameters. These studies suggest that such real-time tuning using the NSOM tip is an attractive method to achieve control on active photonic devices.