Plasma and thermal effects on the performance of high power floating grating DFB laser

Two dimensional finite element analysis of the carrier transport in a 1.55 micrometer floating grating (FG) high power DFB to be used in conjunction with an external modulator as a high bit rate source, has shown that carrier accumulation and crowding for the etch-through grating layers resulted in current being diverted from narrow bandgap sections into the wider band gap sections of the grating. This augments undesirable heating and thermal degradation in laser L-I. To decrease this effect, three changes to the device parameters have been examined. Heavy doping and the use of wider bandgap FG region have been shown to reduce the thermal effects. Thinning the FG layer has little effect. A transfer matrix method (TMM) thermal model has been used to evaluate the performance of the improved structure. The results compared well with measured data and the analysis shows that efficiencies of 0.38 mW/mA and maximum power 100 mW for AR-cleaved are obtainable with the improved FG design.