New method to measure facet reflectivity of antireflection (AR)-coated laser diodes and LEDs

The facet reflectivity of AR-coated laser diodes and LEDs can be obtained by measuring the reflected optical power from the Fabry-Perot cavity formed by the flat end of a single-mode fibre and the diode facet. The relative error is estimated to be less than 10%. The estimation was based on the measurements on a conventional and an AR-coated 1.3 μm InGaAsP BH laser diode and the theoretical consideration of the light beam divergence and the angle misalignment of the cavity.