Angle-dependent structural colors in a nanoscale-grating photonic crystal fabricated by reverse nanoimprint technology

The structural color of angle-sensitive photonic crystals has attracted great interest because of a possible application in visual sensors. The appearance of a photonic crystal is mainly influenced by the optical properties, structural parameters and the observation angle. In this work, an angle-sensitive photonic crystal with nanoscale gratings was fabricated through reverse nanoimprint lithography. The periodicity and the structural color were investigated through measuring reflection spectra. The structural color of the photonic crystal has a period of 90°. Distinctive colors spanning the entire visible spectrum can be seen when the crystal is rotated. In addition, there is a blue-shift of the peak wavelength when the observation angle is increased. An equation for the observed wavelength as a function of the observation angle is proposed.