Nonlinear optical filters and associated methods. In a representative embodiment, a nonlinear optical filter includes a grating and a dye-doped polymer layer coupled to the grating. The dye-doped polymer layer may include ionic self-assembled layers. An associated method includes: providing a nonlinear filter comprising a grating and a dye-doped polymer layer coupled to the grating, directing an input broadband optical wave upon the filter, and backward diffracting the broadband optical wave from the grating as an output narrowband optical wave. The output narrowband optical wave may include a second harmonic beam.