Real time M2 and beam parameter product measurement using GigE CMOS sensors

Abstract

The ISO 11146-1 standard for measurement of a laser’s M-square requires the minimum measurement of five (5) spatial profiles within the first Rayleigh range and an addition five (5) outside the second Rayleigh range. The first five spatial profiles within the first Rayleigh range establish the beam waist and its location; the second five beyond the second Rayleigh range establish the divergence or convergence from the focusing lens for the M-square computation. The majority of methods used to date are all time averaged and as such are incapable of a real time M-square measurement. We present an ISO 11146-1 compliant method for measuring single shot M-square or beam parameter product values or the measurement of continuous wave sources at rates greater than five frames per second utilizing a pair of GigE based CMOS sensors. One GigE CMOS sensor is setup to measure the minimum of five spots within the first Rayleigh range for the establishment of the beam waist and its location. A second GigE CMOS sensor is setup to measure the five spatial profiles beyond the second Rayleigh range for the determination of the beam divergence from the focusing lens. Both GigE cameras utilize optics that passively create multiple spatial time slices of the beam and superimpose these time slices on the CMOS sensor in real time resulting in the ability to make single pulse measurements or continuous wave measurements at speeds of greater than five frames per second with full ISO 11146-1 compliance.