Photodetectors monolithically integrated with optical waveguides: theoretical and experimental study of absorbing layer effects

We present a model for the study of photodetectors monolithically integrated with optical waveguides. We have investigated how an absorbing layer influences the propagation constants of the modes of optical waveguides, by developing a four layer model with refractive indices in each layer. Comparisons with experimental results obtained with devices made in our laboratory and elsewhere show a good agreement. We have used this model to predict and fabricate a short length GaInAs photoconductor monolithically integrated with GaAs/GaAlAs waveguide on GaAs semi-insulating substrate. Experimental results are analysed using this model.