Temperature dependent near-field emission profiles of oxide-confined vertical cavity surface emitting lasers

The near-field emission profiles of oxide confined GaAs vertical cavity surface emitting lasers (VCSELs) with 20μm aperture have been investigated at different operating temperature and different driving current. The subthreshold emission profile provided the information of carrier distributions. At 20°C, a uniform plateau profile was observed at subthreshold emission, which then transferred to a fundamental mode at just above the threshold current. At higher driving current, the fundamental mode evolved into higher order modes due to the spatial hole burning effect. However, at 90°C the subthreshold emission was no longer a uniform plateau profile but showed some locally high gain regions off the aperture center. The subsequent lasing mode profiles showed high order mode in coincidence with these locally high gain regions at 90°C. The higher order mode profiles remained nearly unchanged under different temperature conditions when driving at constant current above the threshold. These locally high gain regions probably caused by the non-uniformity of the open aperture and the current crowding effect. In addition to the spatial hole burning and thermal lensing effect, these locally high gain regions appeared at elevated operation temperature also affected the higher order mode transitions of oxide-confined VCSELs.