Doctor of Philosophy
Electrical and Computer Engineering
Dr. Jayshri Sabarinathan
“Photonic Crystals (PCs)” are dielectric or metallo-dielectric structures with periodic spatial alternations of refractive index on the scale of the wavelength of light. Many optical devices, based on PCs, have been proposed. There are multiple ways by which equal amount of power of incoming signals can be divided into two, three and four output channels; for example using multiple coupled photonic crystal waveguides, directional coupling and cascaded multimode PC waveguides. Ideally, the splitter should divide the input power equally into the output channels without significant reflection or radiation losses and should be compact in size. In this thesis we have proposed different techniques of optical power splitting using (a) Y-junction, (b) PC line defect waveguides integrated with multimode interference (MMI) block, and (c) multiple line defect PC waveguides. The optical modeling of these proposed structures were investigated by finite difference time domain (FDTD) simulation. The goal was to achieve equal power at each output channel with broad spectrum around the target wavelength with low loss.
Using a new design of a 2-D slab based Y-junction scheme, we have achieved 84.4% power output from a 1×2 power splitter and 58.3% form a 1×4 power splitter configuration respectively. Then to improve the power transmission of 1×4 power splitter configuration, we have examined two more structures, one is 2-D slab PC line defect waveguides integrated with MMI block and another which is based on multiple line defect waveguides. The first structure transmits 75.7% power at the output with 46nm broad spectrum for a 2-D slab configuration whereas the second structure transmits 94.9% power at output with 32nm broad spectrum for 2-D configuration.
The advantages of PC line defect waveguides integrated with MMI block for 1×4 power splitter configuration over the Y-junction are ease of fabrication, broad output spectrum and high transmission power. The only disadvantage is the size of the device. The device is somewhat larger than other devices but still compact enough to compete with commercial on chip optical power splitters. In future multiple line defect PC waveguides will probably be able to achieve both compact size and high power.
Dey, Rajat, "Optical Power Splitting Techniques Using Photonic Crystal Line Defect Waveguides" (2011). Electronic Thesis and Dissertation Repository. 192.