Femtosecond-laser-assisted high-aspect-ratio nanolithography in lithium niobate

We report the successful fabrication of high-aspect-ratio lithium niobate (LN) nanostructures by using femtosecond-laser-assisted chemical etching. In this technique, a 1 kHz femtosecond laser is first used to induce local modifications inside the LN crystal. Then, selective chemical wet etching is conducted using a buffered oxide etch (BOE) solution. The etching rate in the laser-modified area reaches 2 & mu;m h-1, which is enhanced by a factor of & SIM;660 in comparison to previous reports without laser irradiation. Such high selectivity in chemical etching helps realize high-performance maskless nanolithography in lithium niobate. In the experiment, we have fabricated high-quality LN nanohole arrays. The nanohole size reaches & SIM;100 nm and its aspect ratio is above 40 : 1. The minimal period of the LN hole array is 300 nm. Our work paves a way to fabricate LN nano-integrated devices for advanced optic and electronic applications. A femtosecond-laser-assisted lithium niobate nanolithography technique is developed. The etching rate is enhanced to 2 & mu;m h-1. The nanohole size reaches & SIM;100 nm and the aspect ratio is above 40 : 1.