A multi-functional 2×2 multimode interference optical switch based on the deep-etched GaAs/GaAlAs optical rib waveguide with spot-size converter is proposed and analyzed by using the variable transformed series expansion method and three-dimensional finite difference beam propagation method.As a result

the present device can operate in various kinds of output schemes including cross and bar state as well as 3dB coupler by controlling the Schottky electrode located in the center of the only multimode waveguide with the advantages of compactness

high design tolerance

and large optical bandwidth.Moreover

the deep-etched optical rib waveguide satisfies the requirement of the accurate self-imaging

greatly reduces the bent loss

and has large cross section under the single mode condition.In addition

the spot-size converter introduced in the ends of the input/output channels can be conveniently coupled with the single-mode fiber.