| Photonic crystal microcavity lasers are attractive optical sources in communication systems because they have several advantages such as lithographically defined wavelengths, small physical size, and low operating power, compared with conventional optical sources. For these sources to find mainstream applications [O'Brien, 2002], they need to be operated at room temperature, and to be pumped the current electrically. To be operated at room temperature, a high thermally conductive heat dissipating substrate is necessary. To be pumped the current electrically, a doped semiconductor membrane is necessary. However, those two constraints complicate the electromagnetics to make reasonably high quality factor (Q) photonic crystal lasers (PCL). This thesis focuses on design issues to make high Q PCL with a heat dissipating substrate and with impurity doping in the semiconductor membrane.; For lasers to lase, the high Q resonant cavity is necessary because the semiconductor material can provide the limited gain. The heat dissipating substrate, which is necessary to operate at room temperature, reduces Q due to substrate loss. One method to maintain a high Q cavity with increased substrate losses, is to increase the traveling distance of photon or to increase reflectivity of the cavity. One way to increase the traveling distance is to increase the cavity dimension. Cavity dimension can be increased by increasing the slab thickness or by increasing cavity core size, and the effect of it on Q was researched. The Q also increases if the reflectivity of photonic crystal increases, and the method to increase reflectivity of PC was researched. The doping is necessary to make electrically pumped device and the effect of it on Q is researched.; The main numerical tools to analyzing PCLs were the finite difference time domain (FDTD), far field simulation, and optimization algorithm. FDTD is needed to simulate the mode of resonant cavity and its basic algorithm, implementation of filter, boundary conditions, and a formulation on Q was presented. Far field calculation is needed to couple the light to optical fiber in communication system. Optimization algorithm is necessary to predict the optimized device structure, and the optimization on y-branch is presented. |
