Temperature-insensitive flexible polymer wavelength filter fabricated on polymer substrates

Temperature-insensitive polymer wavelength filters with silicon nitride gratings were fabricated on a polymer substrate. Polymer waveguides on polymer substrates were fabricated on top of the Si wafer with a water soluble poly(vinylalcohol) (PVA) interlayer between the Si wafer and polymer waveguides. After the completion of the waveguides, the polymer waveguides are separated from the substrate by dissolving the PVA layer to form all polymer waveguides. The novel process provides a way to overcome the problem of the thermal instability of polymer substrate when the polymer waveguides are directly fabricated on polymer substrates. The polymeric wavelength filter fabricated on a polymer substrate exhibits one order of magnitude lower Bragg wavelength shift with temperature than the device on the Si-wafer in the temperature range of 25-70 °C, which is consistent with theoretical prediction.