This thesis is an exploration of numerical modeling and design of intra-cavity frequency doubled green lasers, which is one of the three key light sources in laser display systems. In this thesis the time-domain traveling wave (TDTW) model, which is well developed to model integrated photonic devices, is derived for modeling and design of a new proposed device. The device is based on the intra-cavity frequency doubling of high power distributed Bragg reflector laser diodes (DBRLD) and MgO-doped periodically poled lithium niobate (MgO:PPLN) waveguides. The numerical modeling and design suggest the superiority of the proposed intra-cavity frequency doubled DBR-LD/MgO:PPLN green laser over traditional single-pass frequency doubled DBRLD-LD/MgO:PPLN green laser. A plane-wave based coupled-wave model is implemented to model miniature intra-cavity frequency doubled DPSS lasers. Good agreement between the planewave model and experiment has been obtained. By employing the plane-wave model, we have explained the phase problem in our optical contact Nd:YVO4/MgO:PPLN green laser. Design examples of wide temperature operation of Nd:YVO4/MgO:PPLN green lasers are also completed by this numerical method. Finally, to model high power bulk intra-cavity frequency doubled diodepumped solid-state (DPSS) green lasers, a three-dimensional coupled-wave model is developed and compared with experimental results. A two-dimensional thermal model is incorporated into the three-dimensional coupled-wave equations to model thermal lensing and thermal de-phasing effects in intra-cavity frequency doubled DPSS lasers. The numerical models we developed are validated by the experimental results. / Thesis / Doctor of Philosophy (PhD)

The effect of hot phonons and the influence of macroscopic polarization-induced built-in fields on the performance of III-V nitride devices are investigated. Self-heating due to hot phonons is analyzed in AlGaN/GaN high electron mobility transistors (HEMTs). Thermal transport by acoustic phonons in the diffusive limit is modeled using a two-dimensional lattice heat equation. The effect of macroscopic polarization charges on the operation of blue and green InGaN-based quantum well structures is presented. To characterize these structures, the electronic part of the two-dimensional quantum well laser simulator MINILASE is extended to include nitride bandstructure and material models. A six-band k.p theory for strained wurtzite materials is used to compute the valence subbands. Spontaneous and piezoelectric polarization charges at the interfaces are included in the calculations, and their effects on the device performance are described. Additionally, k.p Hamiltonian for crystal growth directions that minimize the polarization-induced built-in fields are modeled, and valence band dispersion for the non-polar and semi-polar planes are also calculated. Finally, a design parameter subspace is explored to suggest epitaxial layer structures which maximize gain spectral density at a target wavelength for green InxGa1-xN-based single quantum well active regions. The dependence of the fundamental optical transition energy on the thickness and composition of barriers and wells is discussed, and the sensitivity of gain spectral density to design parameters, including the choice of buffer layer material, is investigated.