Erbium doping of lithium niobate on insulator using low-temperature ion exchange

We propose an optimized low-temperature ion exchange method for fabricating an erbium-doped lithium niobate on insulator (LNOI) substrate. This method ensures the production of high-quality, crack-free substrates. The erbium-doped substrates are characterized spectroscopically in the near-infrared wavelength range. Additionally, we demonstrate deterministic local doping by using a SiO₂ mask. This relatively simple, locally selective doping technology can facilitate the implementation of new and practical active building blocks in the LNOI platform, which could be attractive for several applications, like the realization of integrated lasers and amplifiers.