Ph.D Thesis

Ph.D StudentDery Hanan
SubjectTheoretical Aspects of Carrier Dynamics in Low Dimensional
Semiconductor Lasers
DepartmentDepartment of Electrical and Computer Engineering
Supervisors PROFESSOR EMERITUS Gad Eisenstein
PROF. Bjarne Tromborg


Semiconductor lasers are important devices which serve as the backbone in numerous applications.  The physics of semiconductor lasers has been an extensive research topic for the last three decades. As such, one may be led to believe that semiconductor laser properties are thoroughly understood. However , the vast number of known models are phenomenological in nature and circumvent the need to deal with complex non-linear processes. This limits of course their ability to accurately predict complex laser behavior. Moreover, with technological advances in crystal growth and fabrication techniques, nano scale structures are becoming available and there the need for comprehensive rigorous modeling is imperative.

In this research, we introduce two theoretical aspects of the carrier dynamics in low dimensional (nano scale) systems. First, by employing basic principles of quantum mechanics, we study the sub-one picosecond transient behavior of practical quantum well heterostructures experiencing the passage of an ultra short optical pulse. From details of the carrier distribution evolution, we quantitatively analyze the spectral hole burning effect while including aspects of the energetic structure diagram .

The second issue deals with quantum dash assemblies. We analyze the static and dynamical properties of these new devices, while focusing on effects resulting from the inhomogeneous broadening and the carrier capture process. Our models characterize the wire-like nature of these media and shed light on their dynamical properties. Moreover, our models enables to design nano-structure lasers for high-speed applications as it calculates correctly the effect of the optical gain non-linearities.

In addition, we introduce a comparative model for the optical differential gain in two-, one - and zero-dimensional systems while considering the energy structure and the inhomogeneous broadening. Finally, we present an experimental evidence for the carrier-capture bottleneck phenomena, and show the importance of carrier-carrier scattering in mediating the capture process in nano-structures .