Characterization of an AlGaAs rib waveguide using a grating in a Fabry-Perot étalon configuration

We characterize an AlGaAs rib waveguide using a structure based on a third-order Bragg reflector fabricated by electron-beam lithography. The grating forms a resonant cavity with the sample's uncoated output facet, and we observe a Fabry-Perot étalon behavior superimposed on the Bragg reflector characteristics. We present transmitted intensity measurements as a function of wavelength and temperature. We derive results for waveguide refractive-index profile, loss coefficient, group effective index, effective-index wavelength dispersion, and effective-index temperature dispersion. An auxiliary prism on top of the grating allows us to couple light out of the waveguide into the air. Angular measurements of the outcoupled orders at different wavelengths confirm the wavelength dispersion measurements made on the Fabry-Perot étalon formed by the grating and the cleaved mirror.