Transparent Long-Pass Filter with Short-Wavelength Scattering Based on Morpho Butterfly Nanostructures

We combine the principles of moth-eye antireflection, Bragg scattering, and thin-film interference to design and fabricate a short-wavelength scattering/long-pass filter with sharp cutoff, high transmission of infrared light, and strong reflection of visible light into high angles. Based on the lamellae-edge features on Morpho didius butterfly wings, nanostructures are self-assembled via sequential one-chamber chemical vapor deposition, metal nanoparticle formation, and wet-chemical etching. Finite-element modeling demonstrates strong (>45%) reflection into the first diffracted order for short wavelengths, while retaining >80% transmission for longer wavelengths. Fabricated nanostructures couple more than 50% of reflected light into angles of >10° while enabling broadband long-pass transmission. Such structures have potential applications in light trapping for tandem solar cells, stealth, and signals processing