Using ferrule-top opto-mechanical probes as a new tool in VCSEL reliability experiments.

Today, vertical cavity surface emitting lasers (VCSELs) are used in many high-end applications, for which the laser lifetime is a critical parameter. Changes in the spatial distribution of the various emission modes of the VCSEL can be used as an early sign of device degradation, enhancing the speed and detail of failure mode analysis. We have developed a ferrule-top combined atomic force microscopy (AFM) and scanning near-field optical microscopy (SNOM) probe that can be used to analyze the transverse mode pattern of the 850 nm radiation at a <200 nm spatial resolution. During accelerated lifetime testing, the newly developed method shows that small local changes in the optical output can already be detected before any sign of device degradation is observed with conventional methods.