The problem of edge coupling a double-heterostructure GaAlAs laser diode to a planar titanium indiffused LiNbO3 waveguide has been studied both experimentally and theoretically. Alignment sensitivities (3-dB points) have been measured and found to be ∼15 and 1 μm in the longitudinal and transverse directions, respectively. The dependence of the coupling efficiency on misalignments has been found to be in good agreement with the predictions of a simple Gaussian coupling model. In addition, a prototype coupler has been fabricated in a flip-chip configuration on a silicon substrate with ∼15% coupling efficiency into the waveguide's fundamental mode.
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