THEORY AND EXPERIMENT ON THE AMPLIFIED SPONTANEOUS EMISSION FROM DISTRIBUTED-FEEDBACK LASERS

The amplified spontaneous emission (ASE) of a strained quantum-well di stributed feedback (DFB) laser biased below laser threshold is used to extract the gain and refractive index spectra in a systematic manner, A modified Hakki-Paoli method is used to obtain the gain and differen tial gain spectra, The refractive index change due to carrier injectio n is obtained from the shift of the Fabry-Perot peaks in the ASE spect rum, The measured ASE spectrum, gain, refractive index change, and lin ewidth enhancement factor are then compared with our theoretical model for strained quantum-well lasers, Our model takes into account the re alistic band structure and uses the material and quantum-well dimensio ns directly in the calculation of the electronic and optical propertie s. The theory agrees very well with the experiment.