Modeling and Design of Photonic Crystal Quantum-Dot Semiconductor Optical Amplifiers

A novel design of electrically pumped photonic crystal quantum-dot semiconductor optical amplifiers (PC-QDSOAs) is presented in this paper. Therefore, we design a single-mode flat-band slow light photonic crystal waveguide (SL-PCW) for an InAs/GaAs QDSOA in which the pumping is done by passing a current through a laterally doped p⁺-p-n⁺ structure. In addition, for the first time to our knowledge, we propose a nonlinear state space model (NSSM) for PC-QDSOAs, in which the effects of the SL-PCW dispersion relation as well as the effects of the homogeneous and inhomogeneous broadenings of QDs are considered. To do so, the SL effects on the gain enhancement factor and increase of the optical losses are evaluated by considering the wavelength dependence of the modal confinement factor, the group index dispersion, and the SL-enhanced absorption and scattering losses in the SL-PCWs with QD active region. The gain saturation characteristics and modal gain spectra of the PC-QDSOA are investigated under different conditions including pump current and the amplifier length. Simulation results show that the SL-PCWs can be used to reduce the transparency current of the amplifier by a factor of 20 and even more compared with the conventional QDSOAs based on ridge waveguide structures, and enhance the net modal gain of the QD active region by a factor of two to six over a broad wavelength range of about 62 nm. We found that the power consumption of PC-QDSOAs can be decreased by a factor of about 100, and also the amplifier length can be reduced by a factor of five and beyond, compared with the conventional QDSOAs. The results of this paper are useful for many applications where low power consumption and small size of the optical amplifiers are important.