Theoretical And Experimental Study Of Linewidth Enhancement Factor Of Semiconductor Lasers

A simple model of calculating the linewidth enhancement factor (a factor) is presented based on the theory of Henry. Interband transition, free carrier absorption and band gap narrowing are considered in this model. The a factor is calculated by fitting the photon energy dependence of carrier concentration and differential gain.The gain curves of semiconductor lasers based on GaAs, InP and InAs active region materials are simulated, and the a factor of three semiconductor lasers are investigated. It shows that the effect of free carrier absorption can be ignored for the material with a larger bandgap and effective mass of conduction band when analysing the a factor. Further, the a factor of InGaAs/GaAs quantum well laser is emphatically studied because of its advantages of gain, power and linewidth and its values in many applications. Subsequently discussed in the thesis are three important parameters of InGaAs/GaAs quantum well laser containing quantum well width. In mole fraction and the threshold concentration at different temperatures. The results show that the increasing of well width and In mole fraction leads to increased a factor, and the increasing of threshold concentration leads to decreased a factor.A1.06μm InGaAs/GaAs quantum well laser with a small a factor was designed and prepared by discussing the well width and In mole fraction. The a factor is measured, the experimental results show that the difference between theoretical and experimental values is induced by variation of the lasers temperature and the defects or dislocations in strained quantum well materials.