Recent progress of low-loss silicon nitride waveguide in polymer is presented. The fabrication technology requires only low temperature (<200°C) processes and standard photolithography. These waveguides feature a large geometric aspect ratio, resulting in a strong waveguide birefringence. For the TM mode an average propagation loss of about 0.72 dB/cm is measured, while for the TE mode the value is about 0.96 dB/cm. Also demonstrated are uniform Bragg-grating filters and sampled grating filters. Since the waveguide modes are weakly guided and the majority of light field distributes in the polymer cladding, various optical properties of the polymer materials can be exploited. A thermally tunable waveguide Bragg grating is thus demonstrated, with wavelength tuning range above 57 nm for the TM mode and 49 nm for the TE mode, at a tuning power of about 220 mW.