Innovative Facet Passivation for High-Brightness Laser Diodes
Technical Report,17 Aug 2012,16 Nov 2015
Science Research Laboratory, Inc. Somerville United States
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The objective of this effort is to increase the power of low fill-factor 20 laser diode LD bars from the present state-of-the-art SOA of 60-70 Wbar to operate reliably at 300Wbar. This dramatic 5X increase in the powerbar will be accomplished by increasing the power at which SOA LDs fail, namely, increasing the threshold for catastrophic optical damage COD of the LD mirrors by improving the passivation of the facets. The SOA facet passivation is the E2 passivation that was invented by IBM in the early 1990s. While E2 passivation is perfectly acceptable for SOA bars operating at 60-70 W, it is not capable of withstanding the 300 W20 fill-factor bar desired for military high energy lasers HELs. COD of the front facet laser mirror is the main failure mechanism that constrains scaling LD power by 10X over the SOA to 600 W per bar. COD is due to optical absorption at the facets as a result of dangling bonds resulting from the facet formation process cleaving or from contamination from the ambient.