| Popis: |
Semiconductor lasers with the combination of characteristics such as large output power, single mode operation and good beam quality are very often desired. The photonic crystal surface emitting laser (PCSEL) has shown significant promise and has received much attention with the purpose of achieving devices with the desired characteristics. The evaluation of the resonant modes of the structure is a primary requirement in modelling PCSELs. However, conventional techniques such as PWE, CMT and FDTD are either computationally very time consuming or mathematically rather intensive. The aim of this thesis is to develop a new model for evaluating resonance of 2-D photonic crystal, pertinent to the lasing mode of PCSEL. Such aim is achieved by first studying wave characteristics of 1-D periodic structure and understanding the eigenmode and eigenfunction of both infinite and finite periodic structure. It is shown that the eigenmode of the infinite periodic structure is the Bloch mode while the eigenmode of the finite periodic structure is represented by optical tunnelling type of solution. The solutions correspond to the characteristic impedance of the periodic structure. The concept of eigenmode of finite periodic structure is then used to establish the 2-D model of photonic crystal. The essential underlying concept of the analysis procedure presented in this work is based on viewing the 2-D photonic crystal as a laterally periodic multilayer waveguide which is longitudinally segmented. Such model matches with conventional model favourably and proved to be versatile, efficient, fast (for 500×500 periods takes ~7min using laptop: 2 core at 1.70 GHz, negligible memory usage. (Compare to FDTD for 20×20 periods takes 5h using supercomputer system: 12 core, 24GB RAM). Thus, the model has the potential of generating more comprehensive models of photonic crystal based devices. Experimental work including fabrication, characterisation further proved the validity of the model. PCSEL with external reflection is experimental studied. It is shown that the lasing characteristics can be modified through introduced external reflection. |
