Tunable guided-mode resonant filter with wedged waveguide layer fabricated by masked ion beam etching

A compact, tunable guided-mode resonant (GMR) filter whose spectral reflectance wavelength varies as a function of the spatial position on the device is experimentally demonstrated. The filter incorporates a wedge-shaped waveguide layer that is fabricated using masked ion beam etching (MIBE) technology. A ceramic plate mask consisting of an isosceles triangular window is placed between the ion source and the sample to achieve different etching times at difference locations on the film. The increment in the magnitude of the film thickness is approximately 50 nm over a length of 33 mm, which results in a primary reflectance peak whose spectral location spans the range of 684.2-725.3 nm. The device is designed using the rigorous coupled-wave analysis (RCWA) method, and the proposed device is directed toward the practical application of GMR tunable filters.