Independent transmitted and reflected colors enabled by Fano resonant optical coatings

Conventionally, optical coatings transmit and reflect the complementary colors due to the limitations of the resonant modes in multilayered structures. Here, we experimentally demonstrate a type of semi-transparent optical coating that can produce the same color in transmission and reflection based on Fano resonance. The results verify that when the metallic spacer is extremely thin, almost the same reflectance and transmittance spectra can be simultaneously achieved with the efficiency about 40%. Furthermore, we comprehensively explore the change of the colors by varying the thickness of the metal and the refractive index of the dielectric cap. Benefiting from the flexible tuning of the coupled resonator, a broad palette of colors and chromatic information display are presented. Our semi-transparent optical coatings exhibit viewing angle tolerance up to 40 degrees, which may lead to novel display and optical anti-counterfeiting techniques.