氮化鎵二維光子晶體面射型雷射之雷射行為研究

Abstract

本篇論文旨在探討不同的光子晶體週期造成不同特性的氮化鎵二維光子晶體面射型雷射。根據光子晶體週期性結構的布拉格理論，光子晶體的雷射出射必須滿足特定的布拉格繞射條件。因此我們利用平面波展開法模擬TE能帶圖設計光子晶體元件之晶格常數範圍從190到230奈米，並且製作光子晶體週期性結構於氮化鎵共振腔發光二極體。藉由脈衝雷射激發，此結構可以激發出光子晶體雷射。從實驗數據研究光子晶體雷射之正規化頻率正好相對於TE能帶圖三個能帶邊界 (Γ1，K2，M3) ，表示雷射只發生在特定能帶的邊界上。將不同的能帶邊界雷射所得的變角度光致發光光譜圖與能帶圖相互比對，直接量測能帶與雷射點的交會，更加證實雷射發生在(Γ1，K2，M3) 此三個能帶邊界。由實驗數據可知，Γ1，K2及M3的出射角度相對於垂直出射角分別為0˚, 29˚及59.5˚；Γ1，K2及M3的雷射極化程度和發散角分別為 (33%, 35%, 55%) 及 (1.2˚, 2.5˚, 2.2˚) 。此外，我們觀測到Γ1模態的遠場為對稱圖形，正好與光子晶體的對稱型結構相符。由於氮化鎵光子晶體雷射具有許多優越的光學特性，我們相信此結構可以應用在可見光及藍紫光雷射等高功率、大範圍及多用途之光電元件中。

In this thesis, we investigated the different lasing behavior of GaN-based 2D photonic crystal surface emitting lasers (PCSELs) according to different photonic crystal (PhCs) lattice constant. Based on the Bragg theory for PhCs period structure, the lasing behavior could only happen when the Bragg condition is satisfied. Therefore, we simulated the band diagram of TE mode by plane wave expansion method, designed the PhCs lattice constant ranging from 190 to 230 nm, and fabricated the PhCs period structure on our novel GaN-based resonance cavity light emitting diode. By the excitation of pulse laser, the PhCs lasing action is achieved under the optical pumping system. Normalized frequency of investigated PCSELs lasing wavelength can be correspond to three band-edge frequencies (Γ1, K2, M3), which indicates the lasing action can only occur at specific band-edges. We also measured the angle-resolved μ-PL diagrams of different lasing modes. The results further confirmed the lasing modes existed at different band-edge (Γ1, K2, M3) and emitted different lasing angles by mapping the diffraction patterns of band structures and the Bragg theory. From our experiment results, the three band-edge frequencies including Γ1, K2, and M3 has different emission angles corresponding to the normal direction (0˚, 29˚, 59.5˚), respectively. Moreover, the far field pattern of Γ1 mode we observed is symmetric due to the PhCs’ symmetric pattern structure. Besides, the degree of polarizations and divergence angles of Γ1, K2, and M3 modes laser are about (33%, 35%, 55%) and (1.2˚, 2.5˚, 2.2˚), respectively. Overall, according to the superiority features of GaN-based PCSELs, the structure can be applied in the visible and UV laser and become the highly potential optoelectronic device in high power emitter applications.