Reliability performance of 25 Gbit s_(-1) 850 nm vertical-cavity surface-emitting lasers

摘要

Multimode 850 nm vertical cavity surface-emitting lasers (VCSELs) suitable for high bit rate operation are studied. VCSELs with oxide aperture diameters of 5-7μm show a high - 3 dB modulation bandwidth (～20 GHz) and D-factor (～ 8 GHz mA~(-1/2)). To allow low capacitance a multiple layer oxide-confined aperture design was applied. Eye diagrams are clearly open up to 35 Gbit s_(-1) at the temperature of 25℃. Using 35 μm diameter PIN photodiodes and 6 μm oxide aperture diameter VCSELs error-free 25 Gbit s~(-1) (defined as a bit error ration of ≤1× 10~(-12)) optical fiber communication links were tested over 100 m of standard OM3 multimode optical fibers at 25℃ and 85℃. The received optical power for error-free operation was below -4 dBm at both temperatures. A VCSEL reliability study at 95℃ was performed at the high current densities (～18 kA cm~(-2)) needed for error-free 25 Gbit s~(-1) operation at elevated temperatures. After 6000 h a slight increase (less than 5%) of the output optical power at a constant current was observed and most likely due to an ohmic contact burn in effect within the first 2000 h of the study. The results clearly indicate that 25 Gbit s~l 850 nm oxide-confined VCSELs with a complex AlGaO multilayer aperture design and with step-graded Al-compositions have the potential for reliable operation.