Design, fabrication and characterization of photonic crystal based taper

Abstract

Efficient tapers that match the compact modes of photonic crystal (PhC) waveguides to the larger modes of ridge waveguides or optical fibers are key building blocks for matching PhC based devices to standard optics. We have investigated the design, fabrication and measurement of PhC tapers and waveguides. The photonic crystal structures are all based on a triangular lattice of air holes in an AlGaAs/GaAs slab heterostructure. High resolution electron beam lithography together with a combination of dry and wet etching was used to fabricate the structures. The transmission measurements of the waveguides and tapers was carried out by the end fire method. A tunable semiconductor laser with a tuning range from 1240 nm to 1347 nm was used as a light source. The TE polarized light was launched into the waveguide from a polarization maintaining lensed fiber. The losses were determined by two methods that do not depend on a knowledge of the coupling efficiency between the fiber and the waveguide. The first (Hakki Paoli) is based on an analysis of the fringe contrast of the transmission spectrum. The other approach uses a Fourier analysis of the transmission spectrum.