Photopumped operation of dry etched λ=1.5 μm vertical cavity surface emitting lasers

We report on the fabrication of VCSEL mesas for 1.5 μm operation. The single lasers were separated by reactive ion etching (RIE) and 12 μm high mesas with diameters ranging from 3 to 100 μm were formed. The performance of the devices was studied as a function of their size. Photopumped RT-lasing operation of free standing micropost VCSELs was demonstrated, even when using the rather long pulses of a Q-switched YAG laser. The equivalent threshold current density increases with the mesa diameter as a consequence of the difficult heat dissipation in the thin posts. RT operation was achieved with 5 μm diameter free standing mesas (80 ps pulses) and 3 μm wide regrown mesas (250 ns pulses). The quantum well laser showed a very low threshold power of 360 W/cm² (450 kA/cm²). The transverse modes structure was discriminated as TEM₀₀, TEM ₁₁, TEM₂₀ and TEM₁₀. Typically 4-5 transverse modes were observed on 30-100 μm diameter mesas. The threshold increases in the range between -10 and 60 °C with a characteristic temperature around 45 K. Several lasers operated up to 80 °C