Quantum design of a 1.3 μm InGaPAs semiconductor laser
Semiconductor wafer growth can now produce heterostructures of very high quality with stoichiometrically correct growth of individual monolayers. Despite significant advances in MBE and MOCVD growth technologies, a critical void has remained in predicting the performance of final packaged functional amplifier or laser devices. The lack of predictive semiconductor device design and growth monitoring capability can be traced to the extreme complexity of calculating the semiconductor optical response and radiative-nonradiative recombination rates from first principles. Considering the critical role of the above recombination processes in not only, determining gain and slope efficiency but, also all dynamic properties (modulation rates, gain switching, injection locking etc) of SOAs and SLs, it is clear that the impact of this work reaches well beyond the accurate prediction of an L-I characteristic.
Microscopic evaluation of spontaneous emission- and Auger-processes in semiconductor lasers
A fully microscopic approach is used to compute the losses in semiconductor lasers due to spontaneous emission and Auger recombination. The model is based on the semiconductor-Bloch equations and generalized quantum-Boltzmann type scattering equations in the second Born-Markov approximation. As input the theory only needs the structural layout and fundamental bulk-bandstructure parameters. It is demonstrated that such a comprehensive model that calculates gain/absorption, spontaneous emission and Auger processes on the same microscopic level can reliably predict these usually dominant loss processes. Examples of the results are compared to measurements on lasers in the 1.3-1.5 /spl mu/m range demonstrating very good agreement without empirical fitting.
Rational Design, Synthesis and Evaluation of γ-CD-Containing Cross-Linked Polyvinyl Alcohol Hydrogel as a Prednisone Delivery Platform
This study describes the in-silico rational design, synthesis and evaluation of cross-linked polyvinyl alcohol hydrogels containing γ-cyclodextrin (γ-CDHSAs) as platforms for the sustained release of prednisone (PDN). Through in-silico studies using semi-empirical quantum mechanical calculations, the effectiveness of 20 dicarboxylic acids to generate a specific cross-linked hydrogel capable of supporting different amounts of γ-cyclodextrin (γ-CD) was evaluated. According to the interaction energies calculated with the in-silico studies, the hydrogel made from PVA cross-linked with succinic acids (SA) was shown to be the best candidate for containing γ-CD. Later, molecular dynamics simulation studies were performed in order to evaluate the intermolecular interactions between PDN and three cross-linked hydrogel formulations with different proportions of γ-CD (2.44%, 4.76% and 9.1%). These three cross-linked hydrogels were synthesized and characterized. The loading and the subsequent release of PDN from the hydrogels were investigated. The in-silico and experimental results showed that the interaction between PDN and γ-CDHSA was mainly produced with the γ-CDs linked to the hydrogels. Thus, the unique structures and properties of γ-CDHSA demonstrated an interesting multiphasic profile that could be utilized as a promising drug carrier for controlled, sustained and localized release of PDN.