A Study Of All-optical Switch Based On One-dimensional Photonic Crystals With Quantum Dots Defect Layers

All-optical switch is the key device to achieve the fast, transparent and none-block optical information switching of the all-optical communication network, also the basic device for optical computation and interconnection. As the rapid development of the optical communication technology, the demand for ultrafast switches in the net nodes becomes increasingly urgent. The novelty all-optical switches have attracted more and more interests because of the fast response and excellent optical characteristics.All-optical switches utilize the interaction between photons and medium completely to control the photic transmission state, meanwhile, the photonic crystal is one kind of man-made photonics material with spacial periodic variation of refractive index, it has unique photonic bandgap and photon localization, so it's an important basic to realize the function of all-optical switches.In this article, an all-optical switch was proposed based on the one-dimensional photonic crystal (1DPC) contained quantum dots (QDs) defect layers. In terms of the evident exciton of the QDs layers in the room temperature and the optical stark effect pumping the exciton below the resonance, this switch is able to avoid the limitation of carrier accumulation and to response in the pump-pulse-width time. The tiny variation of QDs layers refractive index due to the pump light will change the positions and the resonant transmission peak of defect modes, which could be recovered after the pump pulse rapidly.We discussed the optical characteristics of the single QD and the ensemble of QDs. Using the transfer matrix approach, we discussed the optical bandgap and defect modes of this photonic crystal, established the model of the all-optical switch, and discussed the performance parameter of this switch affected by the number of plies, intensity of pump light and the incidence angle of signal light. Theoretically, we can conclude that this switch has low insertion loss, good contrast ratio and fast switching speed in ps degree; it can work at room temperature hopefully in ultrafast optical communication. At last, we introduced the excogitation for all-optical signal processing based on QD SOA- Mach-Zehnder interferometric. It is expected that our theory and conclusions are helpful as a reference in the designs and experiments of future practical optical switches.