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

In this study, GaN-based photonic quasi-crystal surface emitting lasers (PQCSELs) operated at different Γ 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 Γ 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/cm2 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 Γ band to the lower Γ 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.