Detection of laser induced plasma with interdigital electrodes in laser material processing

Abstract

Laser material processing has attracted great attention in the laser industry due to its ability to process various materials, high operating speeds and precision. However, optimal processing conditions are still underdeveloped, and a large portion of development is undertaken using trial and error procedures. Real-time process monitoring is one of the key technologies with regard to optimizing laser material processing. An external electric field provides a simple, low-cost method with which to monitor laser-induced plasma during the machining process. In this paper, we propose a new electrode design, i.e. an interdigital electrode, to increase the signal level and detection sensitivity of laser-induced plasma. We show the results pertaining to the detection of laser-induced plasma in the air and with materials. The signals detected by the plane and interdigital electrodes are compared. The results show that the signal detected by interdigital electrodes increases 126% when detecting the plasma in the air while the signal increases by four times in plasma generated with Al 5052.