Strip-loaded waveguides on thin-film lithium niobate realized via multi-photon lithography

Integrated photonics play a pivotal role in the advancement of photonic systems in the future. The key to this lies in the research and development of novel materials and fabrication techniques. Lithium niobate (LN) is a material of particular interest due to its advantageous second-order nonlinearity and electro-optical properties. Conventionally, LN waveguides have been fabricated through multi-step processes involving lithographic patterning and dry etching techniques, which are time-consuming and laborious. In this study, we demonstrate an etchless production approach for strip-loaded thin-film LN waveguides through multi-photon lithography. The propagation losses of the fabricated waveguides are as low as 0.15 dB/cm at a wavelength of 1550 nm, which is comparable to existing etching techniques. The manufacturing approach enables a significantly reduced production time and reuse of the thin-film LN substrate. Specifically, we demonstrate the capability of erasing and reprinting polymer strips, fostering a more sustainable practice in the development of LN-based photonic integrated circuits (PICs). The approach can be transferred to other thin-film platforms and enables easier access to waveguide development, which can propel material research in the context of PIC development.