1201 Machining quality controls in ultrashort pulse laser micromachining on lithium niobate substrates

Abstract

The physical relations between the machining conditions and the surface qualities of machined surfaces are investigated in laser micromachining (direct drawing) on ferroelectric lithium niobate (LN), for high quality fabrication of microstructures on the functional material with brittle nature, as a future manufacturing technology of advanced MEMS devices. Pico second pulsed laser with the wavelength of 1064nm was used, then multiphoton process dominants the laser-matter energy coupling for material removal and generating heat. Quantity of heat was controlled by the energy density ρ(0.1-10 J/cm^2), the pulse shot number N(1-1000), the pulse interval t(0.5-10 msec), the kurtosis of laser spot k(14-22), and the environment (air or water). Heat energy is increased exponentially by ρ, and additively by the pulse shot number N. Hence high quality surfaces are obtained by conditions as low ρ-high N of laser irradiations even the same laser fluence ρ×N. Also, longer t(as cooling periods), lower k(as uniform laser power in the spot) and underwater processing (as hear dissipative medium) are effective for high machining quality.