Design and fabrication of a non-periodic multilayer structure for dual-band reflection at 17.1 nm and 19.5 nm

A dual-band multilayer structure was designed and fabricated to achieve simultaneous reflection at 17.1 nm and 19.5 nm under near-normal incidence. The initial design was based on a periodic multilayer stack, which was subsequently optimized into a non-periodic configuration using a genetic algorithm implemented in the IMD software. Theoretically, the structure exhibits reflectance of 41.5% at 17.1 nm and 42.8% at 19.5 nm. Experimentally, measured reflectance was 15.98% at 17.1 nm and 27.11% at 19.5 nm. Furthermore, proton irradiation tests were conducted on the samples, resulting in post-irradiation reflectance of 14.29% at 17.1 nm and 25.14% at 19.5 nm.