Pion Damage in Semiconductor Lasers

Fully packaged, edge-emitting 1310nm wavelength semiconductor lasers, for use in CMS Tracker optical links, have been irradiated at room temperature with 330MeV positive pions. Measurements of the threshold current and slope-efficiency were made in-situ for pion fluences up to 5.2x10 14 pi+/cm2. A comparison is made between pion damage and neutron, proton and gamma damage in terms of the threshold current increase in the lasers. 330MeV pions are 1.2 times more damaging than 24GeV protons and 3.8 times more damaging than 6MeV neutrons; gamma damage is negligible in comparison to hadron damage. Around 40% of the pion damage anneals in 600 hours at room temperature following irradiation. Higher temperature annealing steps ( 300 hours at 40, 60 and 80 degree C) recover a further 25% of the damage, with no anti-annealing.