From Event: SPIE LASE, 2019
Measuring the profile of a laser beam is of critical importance, especially for high power laser systems. Although different techniques exist to measure the beam profile, owing to the use of optoelectronic detectors or cameras, they primarily work at lower powers and require tapping and attenuating the beam. In this process, there is potential for the diagnostic system affecting the beam quality. In this work, we propose a simple technique which can measure the beam profile at full power using a thermal imager without the need for additional optical components. The method involves taking a thermal image of the beam while it is incident on an absorptive surface such as a thermopile head which is used to measure optical power. In addition, a second image is taken using a focused incidence on the surface at low powers. The second image which is reused provides the point spread function. We then make use of the linearity of the heat equation which allows the deconvolution of the point spread function from the original image to obtain the actual beam profile. In this work, we utilized the technique to directly analyze the beam profile at full power of a 100 W class fiber laser and analyzed deviations from single-modedness. In addition, we utilized offset splices to few-mode fibers to launch higher order modes at the 100W level and demonstrate their direct characterization of multimode nature of the profile. This technique provides a simple alternative, using instruments present in most laser labs for direct, high power laser beam profiling.
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Binodbihari Panda, V. Balaswamy, Piyush Raj, Monalisa Mallick, and V. R. Supradeepa, "A simple technique for direct, high power laser beam profile measurement using thermal imagers," Proc. SPIE 10899, Components and Packaging for Laser Systems V, 108990S (Presented at SPIE LASE: February 06, 2019; Published: 4 March 2019); https://doi.org/10.1117/12.2510168.