Theoretical Simulation And Fabrication Of Quantum Dot Photonic Crystal Lasers

Photonic crystal(PhC) is the microstructure with periodic distribution of refractive index, which is able to confine the light effectively. In recent years, PhC lasers(PhCLs) attracted considerable interest due to their ultra-high quality(Q) factor, sub-wavelength scaled volume and integration on chips. PhCLs embedded quantum dots(QDs) as gain material are recognized as one of ideal candidates for the applications of integrating on chips, quantum communication and biosensing because of their low threshold current, high modulation bandwidth and low power consumption. This thesis mainly focuses on the reseach work in the subject of “theoretical simulation and fabrication of quantum dot photonic crystal laser”. In theory, the modulation of nanocavity effect on the carrier dynamics, threshold characteristics and 3d B responses in 1.3-mm In As/Ga As QD PhC nanolasers were studied systematically. Meanwhile, two-dimension(2D) Ga As PhC nanocavity with high Q factor and small mode volume is designed and fabricated in experiment. The obtained results and innovations are as follows:1. The nanocavity effect was introduced firstly in a self-consistent all-pathway rate equation model of 1.3-mm In As/Ga As QD PhCLs. The influences of Purcell effect on the spontaneous emission(SE) factor, photon lifetime and SE lifetime were considered. The calculation results shown that high Q factor can lead to the decrease in carrier occupation probability for ground state, and the nonlinear relationship between Q factor and threshold was obtained. An optimized Q factor(~2500) exists for the high speed operation of nanolaser with a bandwidth exceeding 100 GHz, but the lowest energy consumption per bit transmission occurs at a relative high Q factor ~7000.2. The calculation methods of the dispersion relation for PhC structure had been introduced and discussed, and the analysis was focused on the plane wave expansion method and the finite time domain finite difference(FDTD) method. For the FDTD method, the boundary conditions, the setting of excitation source and the stability of calculation had been investigated in detailed.3. A series of processing techniques for the fabrication of Ga As-based PhC nanocavity were investigated systematically, which include electron beam lithography, ICP dry etching and wet etching. The influences of exposure dose, beam speed and step size on patterns were analyzed, meanwhile, ICP dry etching and wet etching were optimized for the fabrication.4. PhC nanocacity was designed by using FDTD Solutions. High Q factor PhC nanocacity coupled in array(PCCA) in the shape of an equilateral hexagon was fabricated. The cavity modes and the corresponding Q factor of PCCA structure was investigated by using 3D FDTD. By modifying the radius of six end-holes(photonic barrier) between the two adjacent nanocavities, an optimized high Q PCCA was achieved and in good agreement with experiment results. This result provided a simple and effective way to avoid the deterioration of Q factor of PhC nanocacity coupled array.