Surface Quality Assessment in Femtosecond Laser Micromachining of Glass under Different Ambient Media

Femtosecond laser micromachining (FLM) is an effective technique for generating functional surfaces and microfeatures on glass substrates.However, FLM of glass in ambient air is prone to micro-cracks, debris, and thermal damage in the machined region leading to poor surface quality.The ambient medium used in FLM significantly affects the quality of the machined surface.In this study, FLM of glass is carried out in four different ambient media; KOH, HF, DI water, and ethyl alcohol to compare their effects on the surface quality.The glass substrates were submerged 1 mm below the free surface of liquid media and 300 m wide channels were fabricated by scanning the laser beam of diameter 40 m and 209 fs pulse duration at variable pulse energies.The experimental results show FLM in KOH solution exhibits better surface quality than HF, DI water, and ethyl alcohol.The surface roughness values of microchannels obtained in the KOH solution were the minimum, measured to be 1.125 m at 15 J.Microcracks were observed in the other three media which were most prominent in ethyl alcohol.FLM of glass in KOH is a promising approach for minimizing roughness and thermal damage without much loss of surface integrity.These findings have implications for the development of glass microfluidic devices and other applications that require precise and functionalized glass surfaces.