Small-size taper design based on fourth-order Bezier curve

Taper is a basic device widely used in photonics technology which transmits light between the waveguides with different widths. Tapers are usually designed to be trapezoidal in shape, which is simple but has many limits. If the taper is designed to be too short, the broken lines at the junction positions between the strip waveguides (SWGs) and the taper will excite high-order modes and cause high fundamental mode loss. As a result, the traditional tapers are always with a long length which limits the miniaturization of photonic systems. To solve this problem, we proposed a method based on forth-order Bezier curve that made the taper has both small size and good performances on the transmission loss of fundamental mode and the mode excitation ratios (MERs) of high-order modes. According to the obtained results, the proposed Bezier curve method decreased the length of a taper from 100μm to 30μm on the premise of maintaining the performances.