Metasurfaces with perfect infrared absorption promise integrated filters and compact detector elements with narrowband thermal emission. Phase‐change materials (PCMs) are prime candidates for active, non‐volatile absorption tuning. Commonly, the response of the entire metasurface is tuned, while local adaptions remain elusive. In this work, flexible encoding of different absorption/emission properties within a metasurface is shown. The plasmonic PCM In3SbTe2 (IST) is employed to obtain control over the emissivity by patterning an adaptable grating absorber metasurface. Using a commercial direct laser writing setup, the IST is locally switched from an amorphous dielectric into a crystalline metallic state, and cm‐sized stripe gratings are written above a reflecting mirror. Modification of already written patterns is demonstrated by changing the laser power and thus the IST stripe width to encode different polarization‐sensitive patterns with nearly perfect absorption into the same metasurface. Finally, an apparent local temperature pattern due to the large‐area emissivity shaping metasurface is measured with a conventional thermal camera. The results pave the way towards low‐cost, large‐area, and adaptable patterning of metasurfaces with wavelength and polarization‐selective perfect absorption, enabling applications like enhanced thermal detection, infrared camouflage, or encoding anti‐counterfeiting symbols.
We discuss and describe the development of an origination process for planar free-form micro-optical elements from a given optical design. The targeted masters serve as origination structures for a roll-to-roll mass fabrication process. Specifically targeted are complex, optically smooth, surface relief structures with variable structure heights in the range of 1–20 µm, with typical lateral sizes of more than 5 µm. The area of the targeted masters is in the range of
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. The main part of the paper is devoted to the description of a self-developed grayscale laser direct-write platform enabling one- and two-photon absorption lithography, also in combination on one and the same sample. In the following, we describe both methods and show that both lead to excellent structural quality of surface micro-relief structures. As a showcase of what the system can do in principle, we designed and fabricated free-form micro-optical elements to project light from an LED as a defined light pattern onto a wall. The proper optical functionality of the fabricated element was shown within a demonstrator setup.
We propose an optical setup based on a spatial light modulator to facilitate rapid micro structuring such as laser lithography. The beam shaping of the system was addressed and we were able to minimize the effect of common issues of SLMs by adjusting our optical setup. We separated the zero-order focal plane from the first image plane via a focus shift improve the image quality. This causes a Fourier filtering which is theoretically analyzed. This work explains challenges in filtering the zero-order beam and vali-dates the achievable resolution of ~11 µm of the proposed setup. The speed of maskless structuring can be improved by this approach while maintaining the resolution. We demonstrated the use of the setup for spatial light modulator-based maskless laser lithography.
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