Theoretical And Experimental Investigation On Quasi-3-D Photonic Crystal Waveguide

Since the invention of artificially engineered photonic band gap materials, photonic crystal waveguide (PCW) have been the active research because of their potential to be a basic building block for densely integrated optics. However, how to realize low-loss and large-bandwidth PCW are still a problem.We proposed a novel quasi-three-dimensional (3-D) photonic crystal (PC), which is composed of two-dimensional PC and one-dimensional distributed Bragg reflector structures with a matching layer set between them. Through adjusting the thickness of the matching layer, in-plane confinement by the effects of Bragg grating and total internal reflection can be achieved simultaneously. Using this quasi-3-D PC waveguide structure, a wide transmission band was numerically demonstrated both in GaAs/AlxOy (or Si/SiO2) and GaAs/AlAs material group.We established the numerical methods to model the quasi-3-D PCW with matching layer structure. The numerical results confirmed that, for high-index contrast material group, such as GaAs/AlxOy or Si/SiO2, the low loss single mode transmission band is almost ten times wider than that in conventional PCW structure, while for low-index contrast material group, such as GaAs/AlAs, a wide low loss transmission band is also achieved. These results are very remarkable because radiation modes cannot be suppressed up to now in other PCW structures for the material group with such low-index contrast. The thickness of the matching layer is also investigated and optimized.We proposed the method that through testing the loss of the Bragg waveguide with matching layer at different incident angles to demonstrate the effectiveness of the quasi-3-D PCW with matching layer structure. We fabricated Si/SiO₂ multilayers and Si based ridge waveguide.