Linewidth of 89Х nm-range intra-cavity contacted VCSELs

The influence of the oxide aperture diameter on static and spectral characteristics of 89X nm-range VCSELs with the carrier injection through the intracavity contacts and composite bragg reflectors was studied. Studied devices with apertures smaller than 2 $\mu$m had stable single-mode lasing with the fixed direction of polarization, however for the larger apertures the lasing through multiple transverse modes was registered. It was shown that the increase in laser internal temperature led to the anomalous spectral linewidth broadening. Since active area overheating occurs faster for the devices with smaller aperture sizes, increasing the aperture size allows to reduce the spectral linewidth to 30 MHz with an output optical power of $\sim$1 mW.