Periodic variation of the error characteristics of a compact 1 x 2 opticalpower splitter with the waveguide width

We report, for the first time to our best knowledge, on the periodic variat ion of the width-dependent characteristics, and thus, the optimization of a 1 x 2 optical power splitter. We calculated the error characteristics of t he beat length and the optimum separation distance between output ports for a simple 2-dimensional waveguide structure by using a mode propagation ana lysis for simplicity and accuracy. The optimized interference length and th e separation distance showed periodic variations, which are not expected in a conventional approximation of the self-imaging effect, with the width of the multi-mode interference (MMI) region. The periodicity showed a close r elation to the mode generation period, and the variation was particularly l arge near even-mode generation. When the periodic error characteristics, M ere considered a MMI width of 10 mum showed the best performance for a give n waveguide structure with Delta similar or equal to 0.01. the optimized MM I length and output separation distance were 81.2 mum and 6.1 mum, respecti vely, separation of the output waveguide which were 7 mum longer, and 1.1 m um wider than the conventional MMI design obtained by using a simple SI app roximation. The optimized design provided a minimum total coupling loss of 0.23 dB, 0.14 dB from the input side and 0.09 dB from the output side.