Time-sharing utilization of a high-power pulsed-laser diode for inducing damage and for detecting its threshold level with high sensitivity

This article proposes a method to utilize a commercially available high-power pulsed-laser diode (HPLD) in time sharing to induce damage by laser irradiation and to detect the threshold level of the damage. This method features: (1) damage inducement when the HPLD is under the pulsed high-power laser oscillation mode, and (2) surface reflectivity measurement when the HPLD is under the cw light-emitted-diode illumination mode. This technique allows nondestructive measurement of the damage threshold level with high sensitivity, in spite of its extremely simple approach. Accordingly, the technique is appropriate for real-time inspection in a manufacturing process. The practical data for determining the damage threshold are shown. The damage threshold for aluminum (JIS A5052) was estimated to be approximately 62 mJ/mm 2 . The capability of our proposed method is shown compared with that of more conventional methods. The advantages of our technique are described.