Wide-range angle sensing based on mixed variable line spacing gratings

Variable line spacing (VLS) gratings are core components in spatial spectrum and synchrotron radiation facilities due to their merits of self-focusing, aberration correction, and flat focal field. However, optimal design and fabrication of VLS gratings are still required for matching various applications. Scratch-induced selective wet etching has been proven as a robust way for fabricating various nanostructures because of its simplicity, flexibility, and controllability. In this paper, we proposed convenient and maskless methods to fabricate VLS grating based on scratch-induced selective wet etching. During the etching, key factors, including normal load for the scratching, etching time, and types of etchants, were investigated systematically toward optimizing the process. The shapes including sidewall angle and the bottom curvature of the grating elements can be controlled by adjusting the normal load, etching time and/or etching etchants. It is found that the VLS gratings present a wide-range sensing for angle detection based on the reflection spectrum. Furthermore, combining transferring process, the VLS master gratings could be replicated on polydimethylsiloxane (PDMS) surface, which showed great optical performance. This work opened new light to some extent for the application of angle sensing and structural color showing.