One-step crack-free fabrication of chip-scale lithium niobate through dispersion engineering of femtosecond pulses

Femtosecond-laser micromachining is of tremendous interest to various disciplines including optics, material science, and biomedicine. The continued effort in optimizing laser-matter interactions has, for example, greatly promoted the application of lithium niobite in the fields of nonlinear photonics, on-chip integrated photonics, and quantum optoelectronics. However, fragmentations and cracks commonly accompanying the laser machining process leave the further application of lithium niobate having to face very complicated post-processing procedures. Here, we propose a crack-free micro-structure fabrication method using dispersion-engineered femtosecond laser pulses. This achievement is based on a thorough investigation into the influence of femtosecond laser temporal dispersion on the lithium niobite machining process. We find our approach can improve the terahertz transmittance by about 5.8 times compared to the general case. Our findings may further promote the development of lithium niobite for optoelectronics, integrated devices, terahertz technology, and industrial applications, as well as offer insights into simple realization of precision machining of other forms of hard and brittle materials.