Accurate Measurement of High‑Power NIR Fiber Lasers: Solutions & Best Practices

White Paper: Defense

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As precision demands grow, near‑infrared (NIR) fiber lasers have become indispensable in military, research, and industrial material‑processing sectors.

High‑power continuous‑wave (CW) fiber lasers now deliver from 1 kW single‑mode up to more than 100 kW multi‑mode. Their robust reliability, modular fiber terminations, versatile collimation optics, and interchangeable processing heads (both Gaussian and Top‑Hat) make them the preferred choice for demanding material‑processing tasks.

However, characterizing these powerful beams is not trivial. While conventional thermopile sensors can handle power and energy measurements with water cooling, key parameters—spot size, beam shape, focal position, and M²—require advanced techniques that avoid distortion or damage to the measurement system.

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Overview

In “Accurate Measurement of High‑Power NIR Fiber Lasers,” Yoni Groisman examines the pressing need for precise, practical measurement of NIR fiber lasers that operate around 1070 nm with power levels ranging from a few hundred watts to several kilowatts. Accurate beam characterization is critical for process control and quality assurance in all high‑power applications.

Traditional methods falter when confronted with high power densities that risk sensor damage or beam distortion. The paper outlines three main strategies: (1) indirect imaging of side‑scattered Rayleigh light (e.g., Ophir BeamWatch); (2) pinhole scanning with a single‑element detector, which is bulky and complex; and (3) direct measurement via CCD beam profilers after extreme optical attenuation.

Central to the discussion is the Ophir LBS‑300HP‑NIR, a breakthrough laser‑beam splitter that delivers optical attenuation exceeding one million. By employing paired UVFS wedges, it reflects less than 0.0001 % of the incident beam to a CCD profiler, preserving beam shape, polarization, and minimizing background light. It is rated for up to 5 kW and can handle power densities up to 15 MW cm⁻².

The LBS‑300HP‑NIR features flexible mounting, compatibility with standard C‑mount accessories, and a suite of interchangeable neutral‑density filters for fine‑tuning the intensity that reaches the camera. Validation tests demonstrate clearer, distortion‑free beam profiles compared to conventional attenuators.

Thermal management is essential: the device’s temperature can rise by ~23 °C after 10 minutes of exposure to 4 kW, so active or passive cooling and time limits are recommended to preserve measurement integrity.

Whether used standalone or integrated into larger setups, the LBS‑300HP‑NIR offers reliable, cost‑effective, and precise beam profiling—paving the way for broader adoption of high‑power NIR lasers in industry and research.

References include related literature on high‑power fiber‑laser measurement and Ophir’s BeamWatch and BeamGage systems.