Lasing Characteristics of GaN-Based Photonic Quasi-Crystal Surface Emitting Lasers Operated at Higher Order Gamma Mode

Abstract

In this study, GaN-based photonic quasi-crystal surface emitting lasers (PQCSELs) operated at different Gamma band-edge modes were fabricated and investigated. The photonic quasi-crystal patterns were defined by utilizing electron-beam lithography and inductively coupled plasma etching. Distinctive higher order Gamma band-edge lasing modes were identified in the GaN PQCSELs. The threshold energy density and lasing wavelength for the S3 band-edge mode were 4.6 mJ/cm(2) and 394.2 nm, respectively. The decreasing tendency of the threshold energy of PQCSEL was observed while the designed lasing mode moved from the higher Gamma band to the lower Gamma band. Numerical results showed that the S3 mode had the lower threshold and the threshold gain would be largely varied by tuning the ratio of air hole radius/lattice constant (r/a). Based on calculations and experiments, PQCSELs show the opportunity to realize lower threshold lasers than typical PC laser for specific value of r/a and appropriate higher order band-edge modes.