950 publications from this institution
<title>Abstract</title> Nanophotonics relies on precise nanoscale structuring, yet conventional fabrication techniques remain complex and costly. Layered van der Waals (vdW) materials, with their intrinsic anisotropy and high refractive indices, offer a promising route toward simplified nanostructuring and tunable optical functionality. However, no vdW material has previously been shown to exhibit a strong photorefractive effect—a key requirement for light-based modulation. Here we report a giant photorefractive response (Δ<italic>n</italic> ≈ 0.1) in crystalline arsenic trisulfide (As<sub>2</sub>S<sub>3</sub>), observed even under low-intensity illumination. In addition to refractive index modulation, light exposure enables controlled thickness tuning of As<sub>2</sub>S<sub>3</sub>. The material exhibits a giant photoexpansion of up to 5%, depending on the illumination intensity. Building on this photoexpansion effect, we introduce a maskless, low-cost nanopatterning technique based on continuous-wave laser writing, achieving resolutions up to 50,000 dots per inch without the need for ultrafast lasers. The combination of high photosensitivity, optical anisotropy, and transparency positions As<sub>2</sub>S<sub>3</sub> as a versatile platform for integrated photonics, adaptive optics, data storage, biomedical imaging, and nanoscale sensing.
Plasmonics has established itself as a branch of physics which promises to revolutionize data processing, improve photovoltaics, and increase sensitivity of bio-detection. A widespread use of plasmonic devices is notably hindered by high losses and the absence of stable and inexpensive metal films suitable for plasmonic applications. To this end, there has been a continuous search for alternative plasmonic materials that are also compatible with complementary metal oxide semiconductor technology. Here we show that copper and silver protected by graphene are viable candidates. Copper films covered with one to a few graphene layers show excellent plasmonic characteristics. They can be used to fabricate plasmonic devices and survive for at least a year, even in wet and corroding conditions. As a proof of concept, we use the graphene-protected copper to demonstrate dielectric loaded plasmonic waveguides and test sensitivity of surface plasmon resonances. Our results are likely to initiate wide use of graphene-protected plasmonics.
