Sensitivity to high energy Proton irradiation of 670 nm VCSELs in emitter and receiver mode

Vertical Cavity Surface Emitting Lasers (VCSELs) have recently found increasing interest also for space applications, for example for ultra-compact atomic clocks and intra-satellite data-links. Besides their application as efficient emitters also their application as resonant-cavity type photo-receiver has been demonstrated. The radiation stability of commercial VCSELs emitting at 670nm bas been tested with the exposition to 68 MeV protons with different fluence values up to 10^13 protons/cm^2. Besides the conventional electrical and electro-optical characterization under forward bias conditions, also the reverse bias characteristics up to device breakdown and the receiver characteristics under white light LED illumination have been investigated. Even for the highest proton fluence value only a very small change of the laser threshold current and slope efficiency values has been observed, confirming that these VCSELs can be operated successfully in space or in a high energy physics environment. Regarding their optical receiver properties up to 10^12 protons/cm^2, only a minor decrease of the primary photocurrent was observed. Only for the highest proton fluence a more substantial decrease in open circuit voltage and primary photocurrent and also an increase of the reverse bias current due to defect related tunnelling, before the inset of avalanche breakdown, has been found