We present a new failure analysis technique for dark (optically degraded) vertical-cavity surface-emitting lasers. Measurements of spatially and spectrally resolved light emission under reverse bias provide key information on the failure mechanism.

The need for high bandwidth, high speed interconnects with optimum routing through computer backplanes has led to the use of optical interconnects in multiprocessor computing systems [1]. Most of the current commercially available optical interfaces are based upon 850nm vertical-cavity surface-emitting lasers (VCSELs). Extensive studies conducted by the VCSEL manufacturers show that the reliability of these devices continues to improve [2-4]. In order to understand the risks and implications of using VCSELbased modules in computer systems, we have conducted an experiment designed to provide insight into the emission degradation and failure of VCSEL devices. In this paper we briefly describe the experiment and review the results of the subsequent failure analysis on degraded VCSEL arrays.