Paired interference 3-dB coupler based on SOI rib waveguides with anisotropic chemical wet etching

<正>A 3-dB paired interference (PI) optical coupler in silicon-on-insulator (SOI) based on rib waveguides with trapezoidal cross section was designed with simulation by a modified finite-difference beam propagation method (FD-BPM) and fabricated by potassium hydroxide (KOH) anisotropic chemical wet etching.The- oretically,tolerances of width,length,and port distance are more than 1,100,and 1μm,respectively. Smooth interface was obtained with the propagation loss of 1.1 dB/cm at the wavelength of 1.55μm.The coupler has a good uniformity of 0.2 dB and low excess loss of less than 2 dB.