Title

Theoretical study of quantum well lasers and amplifiers based on the no-k selection rule

Date of Completion

January 2007

Keywords

Engineering, Electronics and Electrical

Degree

Ph.D.

Abstract

The Fermi energy dependent stimulated lifetime and carrier densities based on the no-k selection rule have been used to investigate the characteristics of quantum well semiconductor devices, i.e. semiconductor optical amplifiers (SOAs), linear optical amplifiers (LOAs), distributed feedback (DFB) lasers and quantum well (QW) lasers. ^ A new model for the QW SOA has been developed and confirmed experimentally. The continuity equation for QWs with high carrier densities is combined with the amplifier TW gain equation and Auger recombination and heating effects are incorporated in the model. The operation of the LOA is described in terms of the two mutually orthogonal optical waves in the cavity of a vertical cavity surface emitting laser (VCSEL). An analytical description is developed for both the constant gain region when operated above threshold and for the region of gain compression at higher input power. Also the small signal dynamic behavior and channel to channel crosstalk of the LOA are described by using small signal analysis to evaluate both gain and rate equations. ^ The gain-switched pulse response of VCSELs is measured and compared to an analytical model for gain switching. Using a perturbation technique, a theoretical sech2(t) pulse shape for the photon response is obtained analytically. The condition for obtaining identical repetitive pulses is discussed and found to be determined by both electrical dc bias and ac pulse amplitude and width. The laser RIN is another measurement that provides direct access to the intrinsic laser parameters. The RIN data are analyzed to obtain values of spontaneous emission rate Rsp, which is the controlling factor in many critical laser calculations such as amplified spontaneous emission (ASE) noise, linewidth, coherence, etc. ^ The photon lifetime of the DFB laser is obtained through the relations between cavity photon flux and power associated with the electric fields. The evaluation of both Fabry-Pérot (FP) and DFB modes is performed by the calculation, using two different photon lifetimes, of all modal concentrations, with the Fermi energy as the independent variable. ^