Application of optical emission spectroscopy method for characterization of laser micro drilling

In this thesis work the use of fiber laser source for micro drilling and implementation of Optical emission spectroscopy to characterize laser induced plasma during the process is studied. Commercially pure (cp) grade II titanium is micro drilled using IPG Photonics YLP-50 fiber laser source at SITEC laboratory of Politecnico di Milano. Titanium is chosen as a work piece for the reason it is one of the commonly applicable engineering material in the field of micro drilling for enormous fields like aerospace, automotive and medical. The characterization of laser induced plasma is performed on 1.5 mm thick cp titanium. Approach is with experimental technique in all part of the thesis work. First of all, the fiber laser source is studied which include the temporal behavior and process parameters like pulse width and shape. Secondly, once the laser source and its characteristics are defined, micro drilling process is performed for measurement of drilling time. The main aim of this phase was to understand the process duration and use it to fix gate width for spectrometer. Thirdly, laser micro drilling with spectroscopic measurement setup for optical emission (optical emission spectroscopy) is carried out to characterize induced plasma. Analysis and examination of experimental result using the analytical tool presented was targeting the determination of physical parameters of plasma during micro drilling. Atomic excitation temperature and electron density are the two physical parameters under consideration with the intention of characterizing the temporal behavior, relative amount and distribution of plasma formation. Finally the thesis work presents potential further implementation of the technique used in laser induced plasma for process characterization and monitoring in laser micro drilling.