Complex Fourier Surfaces by Superposition of Multiple Gratings on Azobenzene Thin Films

Abstract

Diffractive optical elements (DOE) are integral components for lightweight and ultra-thin optical elements due to their ability to manipulate light efficiently and accurately. However, conventional DOEs are static and cannot be altered after fabrication, which hinders their adaptability to changing requirements. To overcome this limitation, the potential of surface patterning on azobenzene thin films to fabricate reconfigurable DOEs is investigated. Using holographic lithography, surface topographies with sinusoidal surface relief gratings (SRG) are created and the superposition of up to 80 SRGs with high accuracy and minimal information loss in subsequent inscriptions is demonstrated. This is enabled by a surface patterning tool combining holographic lithography and digital holographic microscopy. Reconfigurable and adaptive optical elements can improve the efficiency of optical coupling and increase the sensitivity and selectivity of sensors, especially in applications such as near-eye displays and plasmonic sensors. These results demonstrate the ability to create complex azobenzene-based DOEs for advanced photonic applications, where the ability to alter optical elements is of high importance.