Measurement of laser beam spatial profile by laser scanning

Abstract

In several undergraduate courses related to laser physics and optics it is crucial that students should be able to understand basic concepts of laser beam propagation. In addition, experimental activities focusing on capability building in photogrammetry and remote sensing technologies are considered essential for geoinformatics undergraduate studies and for sustainable development of geospatial sciences. The understanding of laser beam scanning technologies and the fundamental physics of laser beam propagation are key factors in order to awaken students’ motivation to study remote sensing technologies. Recent advances in CCD sensors and beam profiler systems have made the measurement of laser beam spatial profile easy and accurate. However, an experiment based solely on a beam profiler could have lower pedagogical impact than expected, especially in the case of courses where scanning technology understanding is considered fundamental. With this in mind, we propose a straightforward laboratory experiment based on a modified pinhole technique where instead of using a spinning blade or a pinhole to cut the beam, a galvanometer scanner is employed to drive the laser beam through a small pinhole and record its intensity passing with a photodetector. Students are able to visualize the spatial profile of a laser beam, calculate the beam width and divergence and compare their results with direct measurement with a CCD sensor. The capability to efficiently control the scanning mechanism and take simple measurements of the spatial profile of the beam can significantly help the educational process toward the examination of more complex issues of remote sensing technologies.