CinSquare M² measurement Tool
The CinSquare is a fully automated M² measurement system to measure the beam quality of CW and/or pulsed laser systems from the UV to SWIR spectral range. The system consists of a fixed focusing lens in front of a motorized translation stage carrying the camera-based CinCam CCD/CMOS/InGaAs beam profiler. Its operational robustness and reliability ensures continuous use applications in industry, science, research and development.
How does the M² measurement system work?
According to ISO 11146-1/2 the CinSquare system measures the complete beam caustic and determines M², waist position, divergence, etc., related to the reference plane. To facilitate its use, the CinSquare M² measurement system is equipped with two alignment mirrors for exact positioning of the laser beam and a filter wheel for incremental beam attenuation.
CinSquare M-squared measurement tool is customizable for specific wavelengths, beam sizes and M² values.
How is M² measured?
Siegman’s proposal became popular because of its simplicity, but experimentally it isn’t so straightforward, and some uncertainties arise from these principles. For example, if you want to measure the waist radius in the lab, how can you be sure that your measurement device is positioned exactly at the focus?
And how far do you need to go to be in the far field to measure the divergence? Are these two data points enough? The folks at the International Organization for Standardization, or ISO, decided to put an end to all this confusion, so they wrote a norm explaining how to measure and calculate M2, properly: ISO 11146.
The ISO norm explains a method to calculate M² from a set of beam diameter measurements, in a way that minimizes sources of error. Here are the main steps:
- Focus it with an aberration-free lens
- Use the regression equations detailed in the norm to fit a hyperbola to your data points for both the X and Y axes. This improves the accuracy of the calculation by minimizing measurement error.
- From this fit, extract the values for θ, w0, R and M², for each axis.
The ISO norm also states a few extra rules about the measurement of diameters (especially when using array sensors such as CCD or CMOS sensors):
- Use a region of interest of 3 times the diameter
- Always remove the background noise before taking a measurement
Learn more about M² measurement and laser beam profiling applications with our application page.