Assigning error to an M<sup>2</sup> measurement

T. Sean Ross

doi:10.1117/12.640434

22 February 2006 Assigning error to an M² measurement

T. Sean Ross

Proceedings Volume 6101, Laser Beam Control and Applications; 610108 (2006) https://doi.org/10.1117/12.640434
Event: Lasers and Applications in Science and Engineering, 2006, San Jose, California, United States

Abstract

The ISO 11146:1999 standard has been published for 6 years and set forth the proper way to measure the M² parameter. In spite of the strong experimental guidance given by this standard and the many commercial devices based upon ISO 11146, it is still the custom to quote M² measurements without any reference to significant figures or error estimation. To the author's knowledge, no commercial M² measurement device includes error estimation. There exists, perhaps, a false belief that M² numbers are high precision and of insignificant error. This paradigm causes program managers and purchasers to over-specify a beam quality parameter and researchers not to question the accuracy and precision of their M² measurements. This paper will examine the experimental sources of error in an M² measurement including discretization error, CCD noise, discrete filter sets, noise equivalent aperture estimation, laser fluctuation and curve fitting error. These sources of error will be explained in their experimental context and convenient formula given to properly estimate error in a given M2 measurement. This work is the result of the author's inability to find error estimation and disclosure of methods in commercial beam quality measurement devices and building an ISO 11146 compliant, computer- automated M² measurement device and the resulting lessons learned and concepts developed.

Citation Download Citation

T. Sean Ross "Assigning error to an M² measurement", Proc. SPIE 6101, Laser Beam Control and Applications, 610108 (22 February 2006); https://doi.org/10.1117/12.640434

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