Ultra-thin deep ultraviolet perfect absorber using an Al/TiO₂/AlN system

An ultra-thin perfect absorber for deep ultraviolet light was realized using an Al/TiO₂/AlN system. The TiO₂ thickness was optimized using the Fresnel phasor diagram in complex space to achieve perfect light absorption. As a result of the calculation almost perfect absorption into the TiO₂ film was found, despite the film being much thinner than the wavelength. An optimized Al/TiO₂/AlN system was fabricated, and an average absorption greater than 97% was experimentally demonstrated at wavelengths of approximately 255-280 nm at normal light incidence. Our structure does not require nanopatterning processes, and this is advantageous for low-cost and large-area manufacturing.