Abstract

This paper investigates the mode conversion in ridge waveguides. Based on the adiabatic mode evolution, several compact adiabatic mode converters with optimized waveguide shapes are proposed. Three types of adiabatic mode conversion from TM to TE modes are proposed. It is found that the designed adiabatic device is greatly shorter than the one based on the linear shape case, but is capable of achieving the same power mode conversion efficiency. Furthermore, an adiabatic TM₀ mode maintaining waveguide taper is proposed to guide the TM₀ mode from narrow waveguide to wide waveguide. The efficiency of the designed adiabatic TM₀ mode maintaining waveguide taper considerably exceeds that obtained with the parabolic design. Then, combining the TE₁ mode to TM₀ mode adiabatic mode converter and TM₀ mode to TE₃ mode adiabatic mode converter, a TE₁ mode to TE₃ mode adiabatic mode converter (which is difficult to design and cannot be achieved even with a linear-shape connection) with a total length of 760 μm and 94% power mode conversion is proposed.

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