Spatially correlated disorder in butterfly wing scales for enhanced light emission and absorption

We investigate the multifunctional optical response of female Papilionoid butterfly wing scales, which have spatially distinct photonic environments that enable emission control and near-perfect light absorption. Atto 633 dye molecules embedded in the white crescent regions of wing scales exhibit modification of spontaneous emission rate with a ∼2.6-fold reduction in emission lifetime. Lifetime reduction is attributed to the local photonic environment, which acts as effective nano-cavities like scattering regions in the wing scale morphology. The two-point correlation function and fast Fourier transform analysis reveal short-range correlations that enable these nano-cavities (sub-micron holes) in white wing scales. However, the black region surrounding the white crescents displays extremely low reflectance, which functions as a near-perfect broadband absorber. The measured total and specular reflectivity spectra demonstrate absorption as high as 98% across the visible range. We use a finite-difference time domain simulation model based on realistic wing geometry to corroborate experimental observations along with wavelength-dependent Poynting vector distribution. Our results establish that the butterfly wing scales are capable of simultaneously modifying the emission rate and achieving near-perfect absorption, offering inspiration for nature-inspired strategies to design multifunctional nanophotonic devices.