Figure 6.

separated by tensile strained barriers of InGaAIAs. Current is injected through a contact pad on the epitaxial mirror and the gold heat sink via the n + doped contact layers [25]. The n-doped epitaxial mirror reflectivity of the front mirror of 99.4% and back mirror reflectivity was 99.9%. The dielectric DBR is combined with an integrated electroplated Au-heat sink and a buried tunnel junction. VCSEL's emitting in the 2 μm region have been demonstrated by the Technical University Munich and commercialised by VERTILAS in the InP material system [25] however the ex-facet power levels from this technology is limited to <1 mW. Due to the very short laser cavity spectral linewidths from VCSEL devices are typically >20 MHz [26], and show high tuning rates of 0.67 nm/mA and 1.5 nm/o C.
