The feasibility of an electrically programmable photonic crystal (PC) is investigated theoretically based on the metal-insulator transition of vanadium dioxide (VO2). We propose a slab structure based on VO2 whose dielectric properties can be modulated by selectively applying the bias on a lithographically defined array of gate electrodes to induce the phase transition. So, unlike the ordinary PCs, wave propagation in the desired structure may be switched on/off or redirected to our satisfaction. To examine the idea, the photonic band structure (PBS) and the wave guiding characteristics are investigated by using the iterative plane wave expansion and the finite difference time domain methods. The results clearly indicate that the changes induced in the VO2 dielectric properties via the phase transition can enable effective modulation of wave propagation at a high speed, offering a promising opportunity for a photonic circuit that can be programmed or reconfigured on demand.
Fundamental electrical and optical properties of strained wurtzite InGaN/GaN-based quantum well light emitting diodes are calculated based on the Rashba-Sheka-Pikus Hamiltonian in the vicinity of the Gamma point. The theoretical results show an excellent correlation with experiments. A novel design of using AlInGaN as quantum barrier is proposed to realize efficient red emission, which is hard to achieve if GaN is used as barrier. To achieve high efficiency, the important factors relating to the oscillator strength are discussed in detail.