More on measuring M2

Feb. 1, 2000
The article "Propagation factor quantifies laser beam performance" (Laser Focus World, Dec. 1999, p. 119) neglects several key issues in the measurement of M2 values.

The article "Propagation factor quantifies laser beam performance" (Laser Focus World, Dec. 1999, p. 119) neglects several key issues in the measurement of M2 values. First by its very composite nature, while the M2 value can be used to compare lasers, it frequently offers little insight into the precise nature of the laser adjustment required to achieve a higher-quality beam. Of greater concern to many users is that the optical setup required to measure lasers is strongly dependent on the laser wavelength, beam diameter, divergence, and approximate M2 value. Thus, marketing pitches notwithstanding, no universal measurement box for all lasers is possible.

Second, pulsed lasers represent a unique challenge to M2 measurement, not mentioned at all by the author. Virtually all M2 measurement systems measure only the average M2 value over a series of pulses—if they can measure pulsed lasers at all. The multiplexed M2 optic we introduced in 1992 was the first to measure a beam at 16 points in space for a single pulse. We simply relied on the long field time (16 milliseconds) of a camera compared to the short (typically nanosecond) pulse length of a laser. This approach allowed pulse-to-pulse variation in M2 in YAG pump lasers to be identified as a contributor to variation in the output of titanium-doped sapphire lasers and nonlinear laser converters.

Finally the author implies that M2 is a complex measurement, yet our $999 LaserTest beam profiler includes an M2 measurement technique compliant with ISO standards that only requires a simple lens to create the beam waist. Even the lens selection is simplified by using a built-in M2 simulator to predict the best lens focal length of a given set of laser parameters.

Gary Forrest
SensorPhysics
Oldsmar, FL 34677
www.sensorphysics.com

Sponsored Recommendations

Brain Computer Interface (BCI) electrode manufacturing

Jan. 31, 2025
Learn how an industry-leading Brain Computer Interface Electrode (BCI) manufacturer used precision laser micromachining to produce high-density neural microelectrode arrays.

Electro-Optic Sensor and System Performance Verification with Motion Systems

Jan. 31, 2025
To learn how to use motion control equipment for electro-optic sensor testing, click here to read our whitepaper!

How nanopositioning helped achieve fusion ignition

Jan. 31, 2025
In December 2022, the Lawrence Livermore National Laboratory's National Ignition Facility (NIF) achieved fusion ignition. Learn how Aerotech nanopositioning contributed to this...

Nanometer Scale Industrial Automation for Optical Device Manufacturing

Jan. 31, 2025
In optical device manufacturing, choosing automation technologies at the R&D level that are also suitable for production environments is critical to bringing new devices to market...

Voice your opinion!

To join the conversation, and become an exclusive member of Laser Focus World, create an account today!