Red VCSELs: More than 4 mW output power at 650 nm

Due to the small bandgap discontinuities and the low thermal conductivity in the AlGaInP/AlGaAs material system the output power of red VCSELs is drastically reduced if the laser wavelength decreases and/or the operation temperature increases. Recently, our group reported the record cw output power of 3.2 mW for 650 nm oxide-confined VCSELs. For high output power and good temperature stability the epitaxial design and the processing have been improved. The epitaxial layer structure has been optimised with respect to doping, interface grading and number of distributed Bragg reflectors (DBR) pairs, on cavity design, number of quantum wells, and alignment of resonator and quantum well wavelength.