Sensitivity of a VCSEL threshold performance to inaccuracies in its manufacturing

The paper describes an impact of various possible inaccuracies in manufacturing of verticalcavity surface-emitting diode lasers (VCSELs), like thicknesses and compositions of their layers different from assumed ones, on VCSEL room-temperature (RT) continuous-wave (CW) threshold performance. To this end, the fully self-consistent comprehensive optical-electrical-thermal-recombination VCSEL model has been applied.

While the analysis has been carried out for the 1.3-μm oxide-confined intra-cavity contacted GaInNAs/GaAs VCSEL, its conclusions are believed to be more general and concern most of modern VCSEL designs. As expected, the VCSEL active region has been found to require the most scrupulous care in its fabrication, any uncontrolled variation in compositions and/or thicknesses of its layers is followed by unaccepted RT CW lasing threshold increase.

Also spacer thicknesses should be manufactured with care to ensure a proper overlapping of the optical standing wave and both the gain and lossy areas within the cavity. On the contrary, less than 5% thickness changes in distributed-Bragg-reflectors are followed by nearly insignificant changes in VCSEL RT CW threshold.

However, exceeding the above limit causes a rapid increase in lasing thresholds. As expected, in all the above cases, VCSELs equipped with larger active regions have been confirmed to require more careful technology. The above results should enable easier organization of VCSEL manufacturing.