Scandium-Doped Aluminum Nitride (AlScN) Thin-Film as a Piezoelectric Optical Waveguide for Photonic Crystal Slabs

Thin-film scandium-doped aluminum nitride (AlScN) combines remarkable properties. Compared to its predecessor aluminum nitride (AlN) it shows an improved piezoelectric effect, a higher second-order susceptibility <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$(\chi^{2})$</tex>, while being optically transparent in the visible spectrum. In addition, AlScN exhibits a rather high refractive index of > 2 within the visible spectrum, similar to dielectric materials such as titanium dioxide, which are often used for photonic components. Since the higher second-order susceptibility is an important parameter for frequency conversion, modulation and optical processing, an increase in research using AlScN for photonic applications is occurring [1]. Further, due the piezoelectrical (mechanical) and optical properties of AlScN it can be used to connect these two realms, as was for example shown by Bian et al. [2].