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Overcoming the Challenges of Measuring High Power NIR Lasers
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Requirements for more accurate processing have turned NIR fiber lasers into a rapidly growing player in all high-power applications, including military, research, and material processing.
The most common types of high-power CW fiber lasers have output powers ranging from 1 kW single mode to over 100 kW multi-mode. Their reliability, flexibility, and wide variety of interchanging fiber terminations, collimation optics, and processing heads (with both Gaussian and Top Hat beam shapes) make fiber lasers most suitable for the material processing industry.
But understanding their behavior can be challenging. While laser power/ energy can be measured by a conventional thermopile sensor with water cooling, other parameters such as Spot Size, Beam shape, Focal position, and M2 require more advanced techniques to measure high power laser parameters without distorting them or damaging the analytical equipment.
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Overview
This document, titled "Overcoming the Challenges of Measuring High Power NIR Lasers" by Yoni Groisman, addresses the need for accurate and practical measurement of high-power near-infrared (NIR) fiber lasers, which have become widely used in material processing, research, and military applications. Modern high-power lasers, especially NIR fiber lasers operating around 1070 nm with power levels from hundreds of watts up to several kilowatts, require precise characterization of beam parameters—including spot size, beam shape, focus position, M², and power/energy—to ensure process control and quality assurance.
Traditional measurement methods struggle with high power densities that can damage sensors or distort beam characterization. The document outlines three general approaches to measuring high-power lasers: (1) indirect imaging of Rayleigh scattered light from the side (e.g., Ophir BeamWatch), (2) scanning with a pinhole and single-element detector, which is complex and bulky, and (3) direct measurement using CCD beam profilers after very high optical attenuation.
The core focus is on the Ophir LBS-300HP-NIR, a novel high-power laser beam splitter designed to enable direct, practical, and highly accurate measurements by providing optical attenuation exceeding a factor of one million. This device uses pairs of UVFS wedges to reflect less than 0.0001% of the incident beam toward a CCD beam profiler, preserving beam shape and polarization while minimizing scattering and background illumination. It supports laser powers up to 5 kW and power densities up to 15 MW/cm².
The LBS-300HP-NIR offers flexible mounting options and compatibility with standard C-mount accessories and comes with multiple interchangeable ND filters to fine-tune the intensity reaching the camera. Validation tests comparing it with conventional attenuators show improved profile clarity and accuracy without beam distortion.
Thermal management is a key consideration, as the LBS-300HP-NIR assembly temperature rises significantly during prolonged exposure to high power lasers (e.g., ~23°C increase after 10 minutes at 4 kW). Thus, it’s recommended to use active or passive cooling and limit measurement duration.
The device can be used standalone or integrated within larger measurement setups, providing reliable, affordable, and precise beam profiling essential for advancing high-power NIR laser applications in industrial and scientific fields.
References include related articles on high-power fiber laser measurement and Ophir's BeamWatch and BeamGage systems.