Resonance waveguide reflectors with semi-wide bandwidth at the visible wavelengths

We present a resonance waveguide grating with relatively wide bandwidth in the visible region of the spectrum compared to typical resonance structures. The reflective properties of the grating are based on amorphous atomic layer deposited titanium dioxide which has rather high refractive index at the visible wavelengths. The resonance grating provides approximately 20-30 nm bandwidth with over 90% reflectance at the visible wavelengths. The measured reflectances of the fabricated elements show also very good agreement with the theoretical predictions. These kind of reflectors may be useful in applications that make use of LED sources.