Albertus Oosenbrug

Power integrity of 980 nm pump lasers at 200 mW and above

More than 50 million device hours have been accumulated to date in field operation of Er/sup 3+/-doped fiber amplifiers (EDFAs) using our single-mode 980-nm semiconductor lasers as pump sources. The reliability of the E2-type pump laser has been reported earlier, and fulfills the requirements posed by terrestrial telecommunications applications, both from wear-out and from sudden-failure rate considerations. Failure analysis results show that most of the device failures are caused by catastrophic rear-mirror damage. This is likely due to the high absorption of the a-Si In the multilayer Al/sub 2/O/sub 3//a-Si stack. To prevent this type of failure mechanism, a rear-mirror stack has been developed in which the absorption has been strongly reduced. In order to test the effect of the reduced back-mirror absorption and the feasibility of operation at 200 mW a large number of E2-type lasers have been subjected to high-current and high-temperature stress tests. The devices used in the experimental work are standard 980 nm E2 lasers, i.e. 750-/spl mu/m long, MBE-grown single-quantum-well AlGaAs/lnGaAs lasers.

Threshold current as acceleration parameter for degradation of 980 nm pump lasers

To experimentally demonstrate reliability beyond levels achieved previously, as required for applications like submarine, one would like to have higher degradation acceleration than available just from temperature and optical power. In particular, this would also be of importance for lot and technology validation. From earlier stress-test experiments, we have evidence that threshold current could be an additional accelerating factor. In this paper we describe the acceleration of the current-degradation rate observed with laser operation at higher threshold-current (I/sub th/) levels. Higher-I/sub th/ devices have been obtained either through selection within a standard population or through modification of the front-mirror reflectivity. The devices used in the experimental work are standard 980 nm E2 lasers, i.e. 750 /spl mu/m long MBE-grown SQW AlGaInAs lasers with a 4 /spl mu/m wide ridge etched into the top p-cladding.