Large-tolerance coherent optical hybrid devices based on polymeric multi-mode interferometer

In this work, a coherent optical hybrid device 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 and the performance-tolerance of MMI is analyzed. Furthermore, to improve the transmission performance, a mode converter design is applied to mitigate the mode mismatch between the self-imaging of the multi-mode waveguide and the single-mode waveguide. The simulation results show a transmission loss below 6.3 dB, a transmission imbalance below 1 dB, and a phase error less than 1°, while the design tolerances in MMI length and width are 40 μm and 0.5 μm, respectively. Then, polymeric optical hybrids devices are fabricated and their transmission properties are characterized. The experiment results in C-band show a transmission loss below 10 dB, a transmission imbalance between 0.5 dB and 1.5 dB, and a phase error less than 10°. The device tolerances in MMI length and width are 25 μm and 0.5 μm, respectively, and both are better than the fabrication tolerances (0.1 μm). The experiment and simulation results match with each other, and substantially meet the practical requirements of the device. This polymeric optical hybrid has low cost and large device tolerance, and is promising to realize highly integrated coherent receiver. ©, 2015, Board of Optronics Lasers. All right reserved.