Quantum dots, Semiconductor lasers
The first part of this dissertation presents a comprehensive study of quantum dot (QD) lasers threshold characteristics. The threshold temperature dependence of a QD laser diode is studied in different limits of p-doping, hole level spacing and inhomogeneous broadening. Theoretical analysis shows that the threshold current of a QD laser in the limit of uniform QDs is not temperature independent and actually more temperature sensitive than the quantum well laser. The results also explain the experimental trends of negative characteristic temperature observed in QD lasers and clarify how the carrier distribution mechanisms inside and among the QDs affect the threshold temperature dependence of a QD laser diode. The second part is on the experimental demonstration of lithographic lasers. Today’s vertical-cavity surface-emitting lasers (VCSELs) based on oxide-aperture suffer from serious problems such as heat dissipation, internal strain, reliability, uniformity and size scaling. The lithographic laser provides solutions to all these problems. The transverse mode and cavity are defined using only lithography and epitaxial crystal growth providing simultaneous mode- and current-confinement. Eliminating the oxide aperture is shown to reduce the thermal resistance of the device and leading to increased power density in smaller lasers. When it is combined with better mode matching to gain for smaller devices, high output power density of 58 kW/cm2 is possible for a 3 μm VCSEL with threshold current of 260 μA. These VCSELs also have gratingfree single-mode single-polarization emission. The demonstration of lithographic laser diodes with good scaling properties is therefore an important step toward producing ultra-small size laser diodes with high output power density, high speed, high manufacturability and high iv reliability. Lithographic VCSELs ability to control size lithographically in a strain-free, high efficiency device is a major milestone in VCSEL technology.
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Doctor of Philosophy (Ph.D.)
College of Optics and Photonics
Length of Campus-only Access
Doctoral Dissertation (Open Access)
Dissertations, Academic -- Optics and Photonics, Optics and Photonics -- Dissertations, Academic
Demir, Abdullah, "New Laser Technologies Analysis Of Quantum Dot And Lithographic Laser Diodes" (2010). Electronic Theses and Dissertations. 1561.
Restricted to the UCF community until August 2010; it will then be open access.