蓝紫光氮化镓光子晶体面射型激光器

摘要

设计、制作了蓝紫光氮化镓光子晶体面射型激光器结构，并测量其光学性质，探讨了光子晶体的晶格常数、边界形状及晶格种类对激光器特性的影响。激光器结构采用有机金属化学气相沉积法配合电子束光刻及感应耦合等离子体干蚀刻等技术制作。由角度解析光致发光系统测得绕射图案、激光发射光谱及发散角等光学性质。同时，使用平面波展开法及多重散射法计算光子晶体的能带结构与阈值增益。由实验结果得出，可由改变光子晶体的晶格常数达到调变激光器操作模态的目的。此外，光子晶体的边界形状对激光器波长及半高宽并无显著的影响，但圆形边界的阈值激发能量密度比六角形边界低0.3 mJ/cm2。另一方面，将六角晶格、四角晶格与蜂巢晶格的晶格种类进行比较，蜂巢晶格具有较小的激发能量密度（1.6 mJ/cm2）及发散角（1.3°），而四角晶格的激发能量密度（3.8 mJ/cm2）及发散角（2.2°）为三者之中最大。多重散射法求得的阈值增益与实验结果相吻合，可视为快速有效设计光子晶体激光器结构的工具。本文研究成果对今后发展高功率蓝紫光氮化镓光子晶体面射型激光器具有指导意义。%We experimentally and theoretically investigate the optical properties of GaN-based photonic crystal surface emitting lasers(PCSELs).We discuss the effects of lattice constant , boundary shape, and lattice type of photonic crystal ( PC) on lasing characteristics .The PCSEL structures are fabricated using the metal-organic chemical vapor deposition , the electron beam lithography , and inductively coupled plasma reactive ion etching technique .The optical properties of PCSEL which include the diffraction pattern , emission spectrum , diver-gence angle and so on are measured by the angular-resolved photoluminescence system .Meanwhile , the plane wave expansion and multiple scattering method ( MSM) are used to calculate the band diagram and threshold gain of PCSELs , respectively .The results reveal that the lattice constant plays an important role in selection of lasing mode .Despite the lasing wavelength and linewidth of circular and hexagonal shapes PCSELs are almost the same, the threshold excitation energy density of circular shape PCSEL is 0.3 mJ/cm2 smaller than that of hexagonal PCSEL . The PCSEL with honeycomb lattice shows the lower excitation energy density of 1.6 mJ/cm2 and divergence angle of 1.3°.In case of square lattice , the excitation energy density is twice as large as that of honeycomb lattice .The overall results show that the single-mode emission , low divergence an-gle , and so on can be produced from GaN-based PCSEL .On the other hand , the numerical results calculated using the MSM are in good agreement with experimental results .The MSM could be a fast and cost-effective approach for predicting the lasing characteristic .We believe that these contributions provide guidance for the development of GaN-based PCSEL .