We propose a novel optical fiber-to-waveguide coupler for integrated optical circuits. The proper materials and structural
parameters of the coupler, which is based on a slot waveguide, are carefully analyzed using a full-vectorial three
dimensional mode solver. Because the effective refractive index of the mode in a silicon-on-insulator-based slot
waveguide can be extremely close to that of the fiber, a highly efficient fiber-to-waveguide coupling application can be
realized. For a TE-like mode, the calculated minimum mismatch loss is about 1.8dB at 1550nm, and the mode
conversion loss can be less than 0.5dB. The discussion of the present state-of-the-art is also involved. The proposed
coupler can be used in chip-to-chip communication.