Instantaneous measurement of M2 beam propagation ratio in real-time

A new instrument design allows the M-2 beam propagation ratio to be measured in real time at the update rate of a standard CCD camera. This allows lasers from single shot to CW to be measured while the laser cavities are being adjusted. This drastically reduces the test time required for this operation. In this paper we will discuss the theory behind this innovative approach to the M-2 measurement and the methods for the selection of the proper optical components for use of the system with various laser types and beam shapes. The authors will show results of numerous measurements of different lasers and laser types, including solid state diode and traditional gas lasers with M-2 Values from near 1 to considerably higher values, and show comparisons these results with other measurement methods. The instrument design is based on a method of simultaneous capture of the waist and several Rayleigh ranges, allowing the instantaneous fit of the ISO M-2 propagation curve. The authors will discuss the important considerations necessary to generate accurate results for different laser configurations.