Highly compact asymmetric Mach-Zehnder device based on channel guides in a two-dimensional photonic crystal.

We have designed and fabricated a 2D photonic crystal (PhC) asymmetric Mach–Zehnder (M-Z) device structure using W1 channel waveguides oriented along $\mathrm{\Gamma }K$ directions in silicon-on-insulator material. The asymmetric structure was designed using a PhC lattice with different filling factors. The asymmetry is obtained as a difference of two periods in the physical path length ($\mathrm{\Delta }L=2a$) between the arms, and it was sufficient to produce a π phase shift in the region of operation around $\lambda =1500\mathrm{nm}$. The asymmetric M-Z structure is more sensitive than a symmetric M-Z structure to changes in the refractive index and therefore becomes an interesting platform for switching and sensor devices.