High wallplug efficiency vertical-cavity top-surface emitting laser diodes

Wallplug efficiencies as high as 12.7% have been achieved for top-emitting VCSELs (vertical cavity surface emitting lasers) by addressing the associated complication of peripheral contacts on proton-bombarded regions in addition to mirror resistance. The two major technical advances that have resulted in the improved wallplug efficiencies are low-resistance p-type DBRs (distributed Bragg reflectors) and low resistance contacts to implanted regions of the DBR. VCSELs designed for 980-nm wavelength have been fabricated from epitaxial material incorporating these advances. Typical device characteristics including 2 mW in the fundamental mode and 2 V thresholds are routinely accomplished. Initially, wallplug efficiencies of 10% were typical; however, subsequent rapid thermal anneals increased the typical efficiency of 11% due to slight decreases in threshold current and slight increases in the initial slope efficiency. The efficiency increased further after an 8 h burn-in at a current of 10 mA. The highest efficiency measured after burn-in was 12.7% and occurred at 1.5 mW in the fundamental mode.