Design simulation and fabrication process of polyimide and polyimide/silica hybrid materials for Rib-type arrayed waveguide grating

This study demonstrated the designed and fabricated results of rib-type polyimide and polyimide–silica hybrid material array waveguide grating (AWG) devices, with refractive indexes of 1.522/1.546/1.522 and 1.4907/1.53/1.4907 as top cladding/core/bottom cladding layers, respectively. Optical measurements indicated that the extinction coefficients of all samples were approximately zero at a 1550 nm wavelength. The coupling losses were−0.74 dB and − 3.28 dB, and the propagation losses were−0.5 4 dB/cm and − 0.21 dB/cm for rib-type polyimide and polyimide/silica hybrid waveguides, respectively. In the micro-compositional and chemical bonding analyses it appeared that the influence of silica content was larger than the Si―N bonds, and silica content played a key role in determining the refractive indexes in polyimide–silica hybrid. It was found that the greater the content of silica the less the refractive index and the less propagation loss when allowing the incorporation of organic polymer networks for reducing light absorption. Meanwhile, the greater nitrogen percentage could contribute to a larger refractive index in polyimide materials.

Research Highlights
► Extinction coefficients of all samples were approximately zero at 1550 nm wavelength.
► Low roughness is suitable for AWG device fabrication with less scattering phenomena.
► Polyimide-silica with more silica reveals less light absorption and propagation loss.
► More silica results in a lower refractive index in polyimide-silica hybrid materials.
► The more nitrogen content in polyimide might contribute to a larger refractive index.