Yttria Stabilized Zirconia (YSZ) valued for its strength, low thermal conductivity, and chemical inertness, are indispensable in high-precision applications such as medical implants, energy and aerospace. Ultrashort pulse (USP) laser machining offers a promising route to produce microstructured advanced ceramics, but realizing its full potential requires a systematic understanding of process variables’ effect on ablation dynamics to minimize micro-cracks and surface melt.

While heat accumulation is widely studied in multi-pulse laser ablation, the effect of pulse interval on ablation efficiency has been under explored. In this study, we investigated the effect of temporal pulse interval on the machinability of YSZ. A femtosecond laser (λ= 1030 nm, pulse duration = 250 fs) was used to fabricate grooves on a flat YSZ surface, which were further characterized using confocal microscopy and scanning electron microscopy. By simultaneously controlling scanning speed and pulse repetition rate (PRR), we maintained constant pulse overlap and varied pulse interval from 1µs to 20µs.

In contrasts with the expected improvement in ablation efficiency due to heat accumulation, at low pulse interval (high PRR), the surface topography of the ablated channels demonstrated an optimal machining efficiency at a pulse interval of 5 µs. This result correlates with the measured ablation threshold as a function of the PRR. In addition, we used thermal simulations to correlate the relationship between lattice heating, optical penetration depth, and the ablation depth.

Our results highlight the need to optimize pulse time interval when machining dielectric materials to achieve high machining efficiency and minimum thermal damage.