Polymeric multi-mode interference based optical 90° hybrid with tolerant performance

The key component of coherent detection is an optical 90° hybrid. In this paper, optical hybrid based on polymeric 2×4 multi-mode interferometer (MMI) is investigated and designed according to the self-imaging effect. The structure parameters of MMI are optimized with respect to the maximum insertion loss, the transmission imbalance and the maximum differential phase error. Then, polymeric optical hybrids are fabricated and measured to verify the simulation. The experiment results show good agreement with simulation, while the hybrid performs well in tolerance. A transmission loss below 10dB, a transmission imbalance between 0.5dB and 1.5 dB, and a phase error less than 10°, while the device tolerances in MMI length and width are 25μm and 0.5μm respectively, both are better than the fabrication tolerances (0.1μm). This polymeric optical hybrid is promising to realize highly integrated coherent receiver because of low cost and large device tolerance.