Si_1−<i>x</i>Ge_<i>x</i> cavity coupling in one-dimensional photonic crystals

Abstract This work calculates the transmittance spectrum in a one-dimensional photonic crystal formed by alternating silicon/germanium layers with Si 1− x Ge x doped defects. Using the transfer matrix method, we calculate transmittance by analyzing the dependence on structural factors such as layer thickness, relative location between defects, and germanium concentration. The results show the existence of localized modes inside the photonic band gap, which exhibit a redshift in wavelengths with increasing material concentration and constant thickness. When the number of layers separating two defects is increased, keeping both the germanium concentration and the thicknesses fixed, the localized modes exhibit a degeneracy that disappears and originates a splitting of the spectral lines if the distance separating the defects is small. This work will contribute to the field of silicon-based optical devices.