Deposition and measurements of electron-beam-evaporated SiO_x antireflection coatings on InGaAsP injection laser facets

In situ-monitored electron-beam-evaporated nonstoichiometric silicon monoxide (SiO_x) antireflection coatings on 1.5-μm laser facets are described. Reflectivities of 0.05% are demonstrated on devices with one facet coated, and mean reflectivities of 0.07% are demonstrated for traveling-wave amplifiers with both facets coated. The polarization-dependent reflectivities were measured at several wavelengths for both device types and were found to be broad-band (R <0.1% over an approximate wavelength range of 400 Å). The reflectivities obtained using measurements of the noise and gain spectra were compared. The use of the noise spectrum was found to underestimate the reflectivities, especially in measurements of the wavelength-dependent reflectivity over a wide wavelength range and in measurements of devices with both facets coated (traveling-wave amplifiers)