A feasibility study on the use of a low-resolution infrared detector array for monitoring the output beam of a high-power laser

The University of Tennessee Space Institute uses a 3kW laser to weld and cut materials. The laser's spot focus distance, spot location, and output changes during a full day of operation potentially producing an uncertain weld strength and a variation in cutting thickness. Therefore, it is desirable to monitor the laser beam output to determine if changes are occurring in the operating Gaussian modes.

This research determined if a 32 by 32 detector array can distinguish between mixed high-order Laguerre and Hermite Gaussian laser beam modes. A software program was written to allow a User to generate Laguerre and Hermite Gaussian beam modes or mixed Laguerre and Hermite Gaussian beam modes with the capability to change the beam size, non-complex amplitude, and rotation aspects. The program further allows the User to display the generated file on a simulated 32 by 32 detector array in black and white or color shades. The program compares single or mixed Gaussian beam modes (reference set) to single or mixed Gaussian beam modes with added Gaussian noise (test sets). A correlation between the reference set and various test sets were performed as an identification method.

It was concluded that the 32 by 32 detector array can determine the dominant Gaussian beam mode operating in a low noise laser. However, identifying other lower amplitude modes is unlikely. In addition, similar modes with rotational differences between the reference and test sets were tested and failed to meet the acceptable correlation criterion.