Tunable Photonic Crystals with Semiconducting Constituents

We propose that the photonic band structure (PBS) of semiconductor-based photonic crystals (PCs) can be made tunable if the free-carrier density is sufficiently high. In this case, the dielectric constant of the semiconductor, modeled as $\varepsilon \left(\omega \right)={\varepsilon }_0(1-{\omega }_p^2/{\omega }^2)$, depends on the temperature $T$ and on the impurity concentration $N$ through the plasma frequency ${\omega }_p$. Then the PBS is strongly $T$ and $N$ dependent; it is even possible to obliterate a photonic band gap. This is shown by calculating the 2D PBS for PCs that incorporate either intrinsic InSb or extrinsic Ge.