Abstract

Very recently, there was a report on the packaging-induced failure (PIF) of high power 980-nm laser diodes.¹ This phenomenon could be regarded as one of the catastrophic optical degradations (COD). The COD was known to be caused by thermal runway process at the mirror facet.² The localized heating of the laser facet due to the high nonradiative recombination leads to narrowing of the bandgap, which results in the increase of absorption coefficient. This causes more heating. This positive feedback eventually leads to melting of the facet. But this does not seem to be the case for PIF. In this work, to understand how the pertinent properties of a laser diode are related to the reliability, general safety criteria against catastrophic optical damage were first derived for a laser diode operating under cw condition. Here, all the equations were motivated close to the facet where surface recombination and optical pumping are the dominant mechanisms. This was done by rescaling of carrier diffusion equations and heat conduction equations with the effective width of the photon absorbing region. The safety criteria could be expressed in terms of operating conditions, laser dimensions, and material properties in analytic form.

© 1994 IEEE