PLANAR MONOMODE OPTICAL COUPLERS BASED ON MULTIMODE INTERFERENCE EFFECTS

The self-imaging property of a homogeneous multimoded planar optical waveguide has been applied in the design of passive planar monomode optical couplers based on multimode interference (MMI). Based on these designs, 3 dB and cross couplers were fabricated in SiO2/Al2O3/SiO2 channel waveguides on Si substrates. Theoretical predictions and experimental results at 1.52-mum wavelength are presented which demonstrate that MMI couplers offer high performance: on-chip excess loss better than 0.5 dB, high reproducibility, low polarization dependence and small device size.