Study of high-speed semiconductor VCSELs based on AlInGaAs heterostructures with large gain-cavity detuning

The effect of the spectral detuning between the spectral gain maximum of an active region based on AlInGaAs nanoheterostructures and vertical microcavity resonance (gain-cavity detuning) on the steady-state- and dynamic characteristics of high-speed vertical-cavity surface-emitting lasers (VCSELs) for the 850-nm spectral range with two selectively oxidized current apertures is studied. For multimode devices with gain-cavity detuning exceeding 20 nm and a comparatively large current aperture ($>$ 6 $\mu$m), anomalous lasing onset via higher order modes is observed, with subsequent switching to lower order modes at high currents. Simultaneous lasing via both types of transverse modes, observed at intermediate pumping levels, leads to a nonclassical dependence of the maximum effective-modulation frequency on the pump current. An increase in the working temperature, as well as a decrease in the size of the current aperture of a VCSEL, leads to classical multimode lasing behavior. The observed phenomena are to be taken into account when optimizing the design of high-speed VCSELs.