A Study Of Ultrafast All-optical Switch Based On Optical Stark Effect In InGaAs/InP MQWs

Optical switches are the key devices in optical communication network which can achieve many functions.As the development of the optical communication the demand for ultrafast switches is increasingly urgent.However the response times of traditional switches are limited due to the carrier recombination lifetime, carrier transit time in the device, and also the external RC time constant. Whereas all-optical switches have attracted more and more interests because of their favorable optical characteristics and much faster switching speed. Therefore in this article, an all-optical polarization switch based on InGaAs/InP multiple quantum wells(MQWs) was investigated and it could be compatible with the optical communication system.This switch by tuning the control pulse near but below resonance dose not suffer from the limitation of carrier accumulation.In the switching process the optical Stark effect is the main term of nonlinear effects. By constructing a theoretical model to simulate the switching action the performance of switch was studied. This switch need high control energy and the insertion loss was also great.Therefore the structure of MQWs was designed over again. The new one takes advantage of the properties of a Bragg-spaced quantum well(BSQW) structure that is grown such that its fundamental Bragg frequency is equal to the lowest exciton frequency of the quantum wells.At this time the photonic bandstructure forms a forbidden gap with both resonance frequencies located within the gap.Such BSQWs have been shown to exhibit large optical nonlinearities and ps recovery times when a spectrally narrow control pulse is tuned within the forbidden gap.The theoretical model of this switch was also constructed. At last some possible develop directions of the switch operating at room temperature were given. It is expected that our theory and conclusions are helpful as a reference in the designs and experiments of future practical optical switches.