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Finite element analysis of a variable optical attenuator based on s-shape polymer waveguide

A variable optical attenuator (VOA) based on S-shape polymer waveguide is demonstrated at the wavelength λ = 1.55 micron. The VOA consists of straight input and output waveguides, an S-shape waveguide and a pair of deposited electrodes. The cladding material of S waveguide is Poly (methyl methacrylate/disperse red 1) (PMMA/DR1) and the core material of S waveguide is SiON. The refractive index of the polymer cladding at S waveguide is modified by the applied electric voltage. Light scatters at the S waveguide and the VOA has large energy loss in the original state at voltage-off. In the voltage-on state, the refractive index of the polymer of the S waveguide reduces, and energy loss changes as the voltage increases. The attenuation of the VOA can be controled and adjusted by the applied voltage. The beam propagation method(BPM) and finite element analysis are employed to simulate and analyse the VOA. The results show that the VOA has large variable attenuation range of 45.2dB and low insertion loss of 0.8dB.