Ultra-fine surface machining of glass using laser-produced charged particles

Ultra-fine machining of glass substrates using charged particles from laser-produced metal plasma is reported. Since the metal target exhibits high efficiency of linear absorption of nanosecond 532 nm laser irradiation, the threshold fluence for machining the glass substrate is lower than 1.2 J/cm2. Pulse energy of 5–8 μJ/pulse is adequate for this high-precision surface machining process. The optimal parameters for the superior quality etching in the glass material was produced using brass plasma at a laser fluence from 3.0 to 4.5 J/cm2 and maintaining the seperation of 20–40 μm between the glass substrate and the metal shim. It is the impingement of the high-temperature, high-speed electrons and low-energy ions in the under-dense region of the laser-produced plasma, rather than high-energy photons, that is responsible for this high-precision machining. If the glass substrate was placed in the over-dense region of the plasma, the high pressure and the shock wave generated due to the interaction causes damage to the machined surface. Our experiments further demonstrate that, using this process, a focused laser beam integrated with a CAD-based scanning motion can be used effectively to generate complex and highly precise microfeatures on glass substrate.