Direct patterning in sub-surface of stainless steel using laser pulses

This paper reports for the first time on the direct creating microcavities in sub-surface of stainless steel using a single Nd:YAG laser pulse. The low peak power density is used in the process, which is in the order of 1 MW/cm(2). The formation of the microcavities in the sub-surface of stainless steel is an evidence of volume expulsion during laser-metal interaction. Direct patterning in the sub-surface of stainless steel is demonstrated by realizing a series of microcavities to form a pre-designed pattern. Potential applications of sub-surface patterning in metal, such as security marking, micro-heater, micro-insulator and micro-sensor, are discussed.