Asymmetric nanocavity: from color-selective reflector to broadband near-infrared absorber

Abstract

Advances in photonics and energy systems increasingly rely on engineering material interfaces to achieve multifunctional performance. In this study, we present a scalable, lithography-free design for asymmetric Fabry–Perot nanocavities (AFPNs) that function as both narrowband visible reflectors and broadband near-infrared absorbers. By utilizing a dielectric–semiconductor–dielectric spacer with silicon as a critical material, we demonstrate tunable color reflection with just a 5 nm thickness variation and over 80% broadband absorption across the 0.8–1.3 μm range. Adding an anti-reflection coating further extends absorption efficiency to near unity while preserving color fidelity. This planar architecture reduces angular sensitivity and eliminates the need for complex nanopatterning, addressing key challenges in scalability and optical efficiency. These findings highlight a versatile platform for optical coatings in display technologies, photovoltaics, and thermal emitters, advancing the design of multifunctional nanophotonic devices.