LIBS applied to control the fabrication process of ridge waveguide on thin films made by fs-micromachining

ROBERTO RAMÓN PEYTON; VALENTÍN GUAREPI; GUSTAVO ADRIAN TORCHIA

São Paulo

Otro; São Paulo School of Advanced Science; 2018

Instituto de Pesquisas Energéticas e Nucleares

Currently, integrated photonic devices are used in many applications. In particular, we would like to stress the great importance they have in optical and quantum communications, among other application. There are different manufacturing techniques; however, direct writing with femtosecond micromachining has some attributes that stand out from the rest. In this sense, the main advantages of the method are: the practicality of building three-dimensional devices, the rapidity with which prototypes are obtained and the variety of materials that can be used. Nevertheless, a significant obstacle in ultrafast laser micromachining is the lack of an on-line diagnostic method to determine the quality of the process.On the other hand, the high-intensity pulses of fs lasers can be used to etch thin films in selected regions through the ultrafast ablation mechanism. This configuration is known as ablated ridge waveguides on planar waveguide substrates. Traditionally, the status of a machining operation is obtained by manual inspection after processing, which limits efficiency and throughput. Feedback from the workpiece under ablation to the laser femtosecond system is thus desirable to precisely control the machining process. One promising technique to address this problem is the use of laser-induced breakdown spectroscopy (LIBS) by which the plasma emission generated, during the laser-material interaction, can be collected and analyzed to identify the elemental composition of the material being ablated, thus it can be used to control the machining process. For example, in the ultrafast ablation mechanism of thin films, many species may appear as characteristic atomic lines, and so, the intensities of each one could be used for improving the quality of the ridge waveguide machining across correlating it with one base spectrum. The figure shows a schematic diagram corresponding to the experimental setup for micromachining.In this work, we use LIBS as a tool to find the machining parameters and a way for on-line measure of the femtosecond laser micromachining process. For this, we will fabricate waveguides in thin films of PLZT on SiO/Si substrate. First, the machining parameters will be obtained, and then, the quality of the waveguides link with the LIBS spectra will be characterized. Finally, a real-time control for the focus position search and feed rate will be implemented, by using the LIBS spectrum correlation as the measured variable.