High quality antireflection coatings on laser facets by sputtered silicon nitride

TLDR: High quality antireflection coatings of laser facets have been achieved using sputtered silicon nitride and similar films were also used to AR coat InGaAs PIN detectors thereby significantly increasing their responsivity.

Abstract: Single-layer antireflection (AR) coating films are used to transform semiconductor injection lasers into different kinds of active device. For example, a laser whose emitting facet reflectivities (one or both) are reduced to zero is transformed into a superluminescent diode or an optical amplifier, respectively. AR coated lasers are also very desirable in various configurations of a laser in an external cavity or as sources for optical fiber sensor applications. High quality antireflection coatings of laser facets have been achieved using sputtered silicon nitride. The emitting facets of InGaAsP lasers at 1.3 and 1.55 μm as well as of AlGaAs lasers at 0.85 μm were coated. The reflectivities achieved were consistently in the 0.01–0.03% range. Similar films were also used to AR coat InGaAs PIN detectors thereby significantly increasing their responsivity.