Optimization of deep-etched, single-mode GaAs/AlGaAs optical waveguides using controlled leakage into the substrate

This paper presents a detailed experimental and theoretical study of the pr operties of deep-etched GaAs/AlGaAs optical waveguides designed using a ver sion of the spectral index method which predicts mode losses due to leakage through the lower cladding into the high index GaAs substrate. By predicti ng and measuring the mode losses due to this mechanism as a function of gui de width, we show that waveguides formed by reactive ion etching through th e core to the lower cladding layer can be both low-loss (0.2 dB/cm) and sin gle-mode even with core thicknesses and guide widths as large as 4.8 and 5. 6 mu m, respectively. We demonstrate the advantages of this type of guide f or making compact integrated optic devices.