Modeling of Process Mechanisms in Pulsed Laser Micro Machining on Lithium Niobate Substrates
Teppei Onuki, Ippei Murayama, Hirotaka Ojima,
Jun Shimizu, and Libo Zhou
Ibaraki University, 4-12-1 Nakanarusawa, Hitachi, Ibaraki 316-8511, Japan
The mechanism behind the laser ablation of LN is investigated using near infrared pico-second-pulsed laser. A model of the mechanism is developed, deriving the mechanical, thermal, and photonic properties of LN in addition to doing preliminary experiments on laser ablation with controlled laser fluence. β is material removal using the nonthermal process via multiphoton ionization, γ is nonthermal material removal with chipping or cracking produced by generated heat (but at temperatures below the melting point), and δ is material removal using the thermal process with temperatures above the melting point, resulting in resolidification at the surface and the adhesion of oncemolten burrs around the processed area. In a process modes map constructed through exhaustive experiments on laser ablation under various irradiation conditions (at specific energy ρ and with number of pulse shots N’), different contributions of ρ and N’ in the machining process are found. In terms of machining quality, desirable conditions in the control of laser irradiations are the use of weaker ρ and increased N’ to keep thermal damage to a minimum and to raise the removal rate.
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