A summary is presented of the combined effects of radiation damage, accelerated annealing and accelerated ageing in 1310nm InGaAsP/InP multi-quantum-well lasers, the type chosen for use in the CMS Tracker optical links. The radiation damage effects are compared for a variety of radiation sources: 60Co-gamma, 0.8MeV (average energy) neutrons, 20MeV (average energy) neutrons and 300MeV/c pions that represent important parts of the spectrum of particles that will be encountered in the CMS Tracker. The relative damage factors of the various sources are calculated by comparing the laser threshold current increase due to radiation damage giving ~0 : 0.12 : 0.53 : 1 for 60Co-gamma, ~0.8MeV neutrons, ~20MeV neutrons with respect to 300MeV/c pions. The effects of bias current and temperature on the annealing were measured and, in all cases, the annealing is proportional to log(annealing time). A bias current of 60mA increases the annealing, in terms of the time taken to anneal a given amount, by a factor of 10 relative to 0mA. The annealing rate is also accelerated by heating the irradiated lasers and recovery occurs ~10 times faster at 60°C than at 20°C. The long-term ageing properties of irradiated lasers were also measured in an accelerated test carried out at 80°C, for 2500 hours, at a bias current of 60mA. No wearout-related degradation was observed in any of the devices. The combined results of these studies have been used to estimate the long-term damage expected for this type of laser operating inside the CMS Tracker. In the worst case of a laser operating at a distance of 22cm from the beam-axis in the forward region of the Tracker, the maximum threshold increase will be ~6mA over the first 10 years of LHC running.
The effect of radiation damage on carrier lifetime in 1310 nm InGaAsP/InP multi-quantum-well lasers irradiated with 0.8 MeV neutrons, was investigated for fluences up to 6.9 X 1014 n/cm2. The damage to the carrier lifetime was studied by measuring the transient response of irradiated lasers to incident optical pulses of 1064 nm and 532 nm wavelength, and by relative intensity noise measurements. The carrier lifetime was determined to be degraded to a similar extent in both the InGaAsP laser cavity and the surrounding InP material following radiation damage.
Radiation damage in 1310 nm InGaAsP/InP multi-quantum-well lasers caused by 0.8 MeV neutrons is compared with the damage from other radiation sources, in terms of the increase in laser threshold current. The annealing behavior is then presented both in terms of both temperature and forward-bias current dependence. The annealing can be described by a model where radiation induced defects have a uniform distribution of activation energies for annealing. This model can then be used to predict the long-term damage expected for lasers operating inside the CMS tracker.
The combined effects of radiation damage and accelerated ageing in COTS lasers and p-i-n photodiodes are presented. Large numbers of these devices will be employed in future High Energy Physics experiments and it is vital that these devices are confirmed to be sufficiently robust in terms of both radiation resistance and reliability. Forty 1310 nm InGaAsP edge-emitting lasers (20 irradiated) and 30 InGaAs p-i-n photodiodes (19 irradiated) were aged for 4000 hours at 80 degree(s)C with periodic measurements made of laser threshold and efficiency, in addition to p-i-n leakage current and photocurrent. There were no sudden failures and there was very little wearout-related degradation in either unirradiated or irradiated sample groups. The results suggest that the tested devices have a sufficiently long lifetime to operate for at least 10 years inside the Compact Muon Solenoid experiment despite being exposed to a harsh radiation environment.
In this paper results from the evaluation and comparison of the analog performance of laser transmitters from several different manufacturers will be reported. The bulk of the tested devices were commercially available InGaAsP edge- emitters (1- and 4-way packages). The evaluation of the lasers is based on a semiautomatic setup that characterizes static properties such as slope efficiency, noise and linearity. The measured data is visualized in a compact way with system pass/fail criteria that enables easy comparison and selection of different laser diodes with respect to system noise, deviation from linearity an operating range.
Karl Gill, Christina Aguilar, C. Azvedo, Vincent Arbet-Engels, Jeremy Batten, Giovanni Cervelli, Robert Grabit, Fredrik Jensen, Chantal Mommaert, Jan Troska, Francois Vasey
Optical data links are being developed at CERN for use in the tracking system of the Compact Muon Solenoid (CMS) experiment to be operated at the future CERN Large Hadron Collider. The radiation environment will be severe in the CMS tracker; simulations predict hadronic fluences > 1014/cm2 over an experimental lifetime of ten years, consisting of a mixture of neutrons, pions and protons over a wide energy spectrum, plus an ionizing dose of approximately 100 kGy. Candidate optical link components must therefore be qualified for sufficient radiation hardness. Results are presented for commercially available InGaAsP lasers and InGaAs p-i-n photodiodes irradiated with 330 MeV pions up to 5.4 X 1014 (pi) /cm2. The evolution of the laser threshold and efficiency with fluence is presented, in addition to the leakage current and photocurrent in the photodiodes. Comparisons are drawn with previous irradiation tests on identical devices using 6 MeV neutrons and 24 GeV protons, and ionizing damage due to 60Co gamma rays.
Several types of commercially available single-mode optical fibers have been irradiated in both gamma and neutron radiation fields to determine the suitability of their use in the readout systems of feature particle physics detectors. A comparative survey of the effect of 60Co gammas and neutrons (<En> approximately 6 MeV) on different fiber types, including standard germanium doped and pure silica core fibers, has been carried out. Selected fibers were further exposed to gamma radiation at four different dose rates to assess dose rate effects. Results are presented for the dose and fluence levels of interest (100 kGy) and 1 X 1014 n/cm2), showing induced losses at 1300 nm to be below 0.1 dB/m for both types of field. It has been seen that the damage mechanism is the same for both fields. We conclude that many modern Ge-doped fibers will be suitable for use in future particle physics applications, which gives greater freedom of choice to system designers, and greater immunity from the problems associated with single suppliers of specific fibers.
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