Optimized inverse design of an ultra-compact silicon-based 2 x 2 3 dB optical power splitter

By combining the finite difference time domain (FDTD) method with inverse optimization algorithm can break through the constraints of traditional design experience and realize integrated silicon components with much more compact sizes. In inverse design process of 2 x 2 3 dB optical power splitter, the direct binary search algorithm is very easy to fall into the local optimal solutions due to its off-centered input and initial refractive index distribution, which limits the performances of the device. In order to address this issue, a two-stage inverse design process is proposed to optimize a silicon 2 x 2 3 dB optical power splitter with compact size of 4.8 x 4.8 mu m which are greatly reduced in size compared to conventional 3 dB optical power splitter. The excess loss and split ratio at 1550 nm are about 1.15 dB and 0.97, which are greatly improved compared to the traditional single-stage inverse design process.