Polymeric variable optical attenuator with a large-core for increased alignment tolerance

摘要

To improve the reproducibility of passive alignment, large core single mode waveguides are demonstrated, which can be connected to thermally expanded core fibers so as to increase alignment tolerance. It is shown that polymer waveguide with a core dimension of 25 μm x 25 μm and an index contrast less than 0.001 can satisfy single mode condition. As a novel functional device incorporating the large core waveguide, variable optical attenuators (VOA) are designed and fabricated. For the fabrication of the thick core structure, a soft molding process is developed. Due to the small index contrast of the waveguide, efficient attenuation is expected for the smaller electrical power consumption, which is confirmed by 3-dimensional beam propagation method. From the fabricated VOA device, more than 20 dB of attenuation is obtained by applying 20 mW.