Lateral lattice shift engineered slow light in elliptical photonics crystal waveguides

A photonics crystal (PhC) waveguide that operates in the slow-light regime is reported in this paper. A second line of circular air holes from the PhC waveguide in a triangular lattice is replaced by a line of elliptical air holes. Based on a three-dimensional plane wave expansion, the lateral shift of elliptical air holes is conducted to enhance the slow-light characteristics. A group index of 166 and a delay-bandwidth product of 0.1812 are derived from an optimized PhC using elliptical air holes with a lateral shift of 160 nm according to the simulation results. A Mach–Zehnder interferometer (MZI) is integrated with the above-mentioned PhC waveguide with a 17 μm length in one of its arms. The measured transmission spectrum of the fabricated MZI embedded with a PhC waveguide shows slow-light interference patterns.