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7 February 2012Reliability study of 1060nm 25Gbps VCSEL in terms of high speed
modulation
Furukawa's 1060nm VCSELs with double-intra-cavity structure and Al-free InGaAs/GaAs QWs enable us to realize
low power consumption, high speed operation and high reliability simultaneously. The power dissipation was as low as
140fJ/bit. Clear eye opening up to 20Gbps was achieved. Random failure rate and wear-out lifetime were evaluated as
30FIT/channel and 300 years.
For higher speed operation, thickness of oxidation layer was increased for lower parasitic capacitance of device.
Preliminary reliability test was performed on those devices. In high speed operation faster than 10Gbps, conventional
lifetime definition as 2dB down of output power is not sufficient due to smaller margin of modulation characteristics. We
suggest threshold current as a barometer for degradation of modulation characteristics. The threshold currents of our
VCSELs degrade small enough during accelerated aging test. We also observed no remarkable change in 25Gbps eye
diagram after aging test. The definition of life time for high speed VCSEL is discussed from the change in threshold
current and so on in addition to the conventional power degradation during aging. It is experimentally verified that our
VCSELs are promising candidate for highly reliable light source including long term stable high speed operation.