Fabrication of Optical Fourier Surface by Multiple-Frequency Vibration Cutting for Structural True Coloration.

Optical Fourier surface is a unique patterned optical surface containing the precise sum of sinusoidal waves, each with a well-defined spatial frequency and amplitude. It can manipulate the desired diffracted light field through its Fourier transform, which brings a straightforward mathematical method for designing complex diffractive optics. However, the fabrication techniques typically have the drawbacks of low efficiency, limiting the large-scale industrial application of optical Fourier surfaces. This study presents a powerful approach, the multi-frequency vibration cutting (MFVC), to enable the high-efficiency fabrication of optical Fourier surfaces. A specific optical Fourier surface consisting of arbitrary frequency components of linear gratings has been fabricated on metallic surfaces using MFVC. Due to the capacity of multicomponent gratings in coupling red, green, and blue lights at the same incident angle, the RGB true color has been prepared. The additive and subtractive principles of mixing the three primary colors are demonstrated. The former relies on the light dispersion induced by grating diffraction, while the latter is based on the light absorption induced by the subwavelength grating-coupled surface plasma polarization (SPP). The experimental results of authentic structural true color on the aluminum surface verify the efficacy of MFVC in the fabrication of optical Fourier surfaces.