Research On Monolithic DBR Tunable Semiconductor Lasers

As increasing demand of the bandwidth of optical communication, optical networks have been developing from static networks to dynamic networks. Not only transmission but also routing function has been integrated into the networks. Tunable lasers with agile and multi-wavelength selective features will be a key component for the optical networks before long. As the research on optical transmission techniques improving, different types of tunable lasers have been developed. Among these types of tunable lasers, DBR tunable lasers are easier to be monolithically integrated and have shorter switching time. These features make them the subject of considerable interest of the research institutes world wide. In this paper, the characteristics of DBR tunable lasers were analyzed based on an appropriate theoretical model. The main contents of this paper are as follows:(1) The gain model of the tunable laser diodes was derived from semiconductor physics. Taking Fabry-Perot structure for instance, the threshold conditions and longitudinal modes were analyzed. Multimode rate equations were introduced to describe the relations between carriers and photons in semiconductor. The calculations of output power and threshold current were obtained from rate equations. The results were bases of modeling the DBR tunable laser diodes.(2) Comparing different modeling methods of tunable laser diodes, we found that matrix based transfer matrix method was more appropriate for the structure of DBR tunable lasers. We made a thorough description of this method in order to make use of it for analyzing the devices. The description includes how to establish, assemble and analyze the transfer matrices.(3) Static tuning characteristics of three section DBR lasers and four sections SGDBR lasers were modeled by the transfer matrix methods. The modeling results include lasing wavelength, output power and threshold current tuning curves of three sections DBR lasers and lasing wavelength tuning curves of four sections SGDBR lasers. All these modeling results were based on and compared with theoretical analysis.(4) Static tuning curves and the multimode rate equations were combined for analysis of dynamics of DBR tunable lasers. The method of optimizing the switching time and decreasing the effect of crosstalk was found by analyzing the transients of different switching currents.