Design and Fabrication of Optical Bandpass Filters for Safe ۲۲۲ nm UVC Light Generation in Medical Disinfection Applications

Introduction: Recent global pandemics have highlighted the urgent need for effective and safe sterilization technologies. Ultraviolet-C (UVC) radiation at a wavelength of ۲۲۲ nm has attracted considerable attention due to its strong germicidal efficacy combined with its limited penetration into human tissues. The generation of safe ۲۲۲ nm UVC light requires optical bandpass filters that selectively transmit this wavelength while suppressing longer, potentially harmful emissions. Material and Methods: In this study, metal–dielectric optical bandpass filters optimized for ۲۲۲ nm UVC applications were designed and fabricated. The design process involved a review of previous studies, material selection, and layer thickness optimization using numerical modeling based on the transfer matrix method. Aluminum was employed as the metallic layer and magnesium fluoride as the dielectric material. The filters were fabricated using physical vapor deposition and characterized by UV–Vis spectroscopy. The effects of deposition errors, post-deposition thermal annealing, and laser damage threshold were also investigated. Results: Several optimized designs for ۲۲۲ nm optical bandpass filters were obtained, offering flexibility based on material availability and desired spectral characteristics. Experimental results demonstrated peak transmission wavelengths close to ۲۲۲ nm with acceptable bandwidths for safe UVC applications. Thickness variations in dielectric layers were identified as the dominant factor influencing spectral shifts, while post-deposition thermal annealing was found to degrade filter performance. The laser damage threshold of the fabricated filters was measured to be approximately ۱.۳ J/cm². Conclusion: The developed metal–dielectric bandpass filters demonstrate suitable optical performance for generating safe ۲۲۲ nm UVC radiation. These findings support the development of reliable far-UVC light sources for medical disinfection applications, contributing to safer sterilization technologies in healthcare and public environments.