Influence of substrate cooling on femtosecond laser machined hole depth and diameter

• Published in: Applied physics. A, Materials science & processing Vol. 89; no. 2; pp. 559 - 563
• Main Authors: ZHENG, H. Y, LAM, Y. C, SUNDARRAMAN, C, TRAN, D. V
• Format: Journal Article
• Language: English
• Published: Berlin Springer 01.11.2007; Springer Nature B.V
• Subjects: Applied physics; Atmospheric temperature; Cooling; Copper; Cross-disciplinary physics: materials science; rheology; Exact sciences and technology; Femtosecond pulses; Laser beams; Laser machining; Lasers; Liquid nitrogen; Materials science; Materials synthesis; materials processing; Physics; Sapphire; Substrates; Scanning electron microscopy; Laser pulse; Temperature effects; Ambient temperature; Laser drilling; Laser cooling; Titanium; Thermal dissipation; Laser beam machining; Copper; Cryogenic temperature; Multiple reflections
• ISSN: 0947-8396; 1432-0630
• DOI: 10.1007/s00339-007-4132-4

Substrate temperature was observed to affect the machined hole depth and diameter during Ti:sapphire femtosecond laser machining of a copper substrate. We studied the blind holes drilled on copper specimens by multiple femtosecond laser (fs) pulses under two temperature conditions, namely the liquid nitrogen temperature (∼77 K) and the atmospheric temperature (∼298 K). Compared to the atmospheric temperature condition, we found that the diameters of the holes are smaller and the depths of the holes are deeper under the liquid nitrogen temperature condition. We attribute the reduction in diameter to the faster heat dissipation of the cooler substrate. We calculated multiple beam reflections in a channel and attribute the increased depth of the cooler substrate to the enhanced multiple laser beam reflections inside the laser drilled hole.