Optimization of geometry of two-dimensional photonic crystal waveguide for telecommunications and sensorics

The results of geometry optimization of the two-dimensional photonic crystal waveguide for minimization of optical losses and stabilization of waveguide modes are presented. The main factor (not including absorption) is the appearance of Bragg reflection. Bragg reflection can be decreased by the decrease of the regions of overlaps with high refractive index in photonic crystal. For this purpose, the holes in photonic crystal can be fabricated not as the whole holes but as the parts of the holes. For waveguide modes stabilization the varying of waveguide width was performed. Computer simulation was performed in Comsol Multiphisics 5.5. Energy zone structure of photonic crystal surrounding waveguide was computed by Bloch functions method. In modeling, the free-triangle grid with quality “extremely fine” was used. The frequency near which eigenvalues were looked for has range of 190–200 THz. For the solving of the problems procedures ARPACK FORTRAN were used which work on base of iteration of Arnoldi (IRAM). Modeling have shown that the used geometrical optimization makes possible to decrease the Bragg reflection by 1.75 times. It was established that the losses of photon crystal waveguide in this case do not exceed 0.4 dB/cm. It was shown that the the decrease in the photonic crystal holes diameter with a constant period of the photonic crystal lattice leads to a decrease in the width of the photonic forbidden bandgap. It was shown also that in the waveguide with optimum width the modulation of waveguide mode is maintained but its amplitude decreases significantly. The obtained results can be used in the development of integrated-optical devices for telecommunications and sensorics with low optical losses.