Impact of cavity tuning on lasing characteristics for GaN-based vertical-cavity surface-emitting lasers

We demonstrated that cavity tuning—i.e., the alignment of a resonance wavelength relative to a distributed Bragg reflector (DBR) center wavelength—is a key factor influencing the laser characteristics of GaN-based vertical-cavity surface-emitting lasers (VCSELs) with AlInN/GaN DBRs. By utilizing in-plane cavity tuning variation across our VCSEL wafer, the effective mirror loss was monotonically increased from 25 to 50 cm−1, resulting in corresponding changes in differential external quantum efficiency, threshold current density, and wall plug efficiency (WPE). The in-plane cavity tuning variation was effectively utilized to extract the internal parameters and identify an optimal mirror loss for high WPE in our GaN-based VCSELs. As a result, an internal loss of 11 ± 6 cm−1, an injection efficiency of 85% ± 10%, and an optimal mirror loss around 40 cm−1, achieving a WPE over 25%, were obtained.