Blue-Violet GaN-based photonic crystal surface emitting lasers

Abstract

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,divergence 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 ofhexagonal PCSEL. The PCSEL with honeycomb lattice shows the lower excitation energy density of1. 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 angle,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.