The optical matrix switch is one of the key devices for future photonic switching systems. Several kinds of discrete semiconductor optical switches have been studied. However, up to the present, only a few investigations have been made on the integrated semiconductor matrix switch. The authors have recently realized integrated 4×4 GaAs/AlGaAs optical matrix switches constructed from 12 electrooptic directional couplers. In order to achieve uniform device characteristics, molecular beam epitaxy (MBE) and reactive ion beam etching (RIBE) were chosen as crystal growth technique and waveguide fabrication technique, respectively, in addition to the simplified tree structure as a matrix switch architecture. As a result, matrix switches with quite uniform device characteristics, such as small switching voltage deviation of 9.0 ± 0.5 V for ⊗ state and 21.9 ± 1.5 V for ⊖ state and little path dependence in ±0.5-dB propagation loss, have been realized for the first time.
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