Laser facet passivation
Effective passivation of laser facets is the key to obtaining the highest power output of edge-emitting lasers
Edge-emitting laser diodes emit very high optical powers from small emission areas, therefore, the optical intensity at the front facet is extremely high. A lot of heat is created in the front facet, where (in addition to normal operation) large numbers of photons are absorbed by different defects including dangling bonds, threading dislocations, amorphous native oxides, or in a short high level of surface states defects. This absorption leads to heating of the semiconductor which shrinks the LD bandgap, resulting in an ever increased absorption and a further shrinkage of the bandgap. This thermal runaway process ultimately melts the semiconductor in what is known as Catastrophic Optical Damage, or COD. Increasing the power threshold at which the COD happens is an important goal for laser manufacturers.
A currently available method that provides the best passivating effect is cleaving laser bars in UHV conditions followed by passivating protection, i.e. ZnSe layer, prior to the deposition of the mirror layers. A significant disadvantage of this approach is the difficult and very costly implementation of the cleaving step performed in the UHV.
With our novel solution laser bars are cleaved in-air, after which treated with an optimized in-situ cleaning process. Once a good clean facet is obtained, the laser bars are passivated in highly controlled conditions before applying the mirror coatings. This way, we achieve results similar to the best processes currently available in the market at significantly reduced costs.
Kontrox increases photoluminescence emission intensity monitored directly from the laser facet active area. This indicates the improvement of surface quality due to defect density reduction enabled with Kontrox.
Passivation of sidewalls
for III-V based MESA structures
In optoelectronic devices, surface recombination and leakage of carriers impose serious limitations on the efficiency of semiconductor devices. Kontrox prevents this from happening.