High-Power Laser Applications

Summary

High-power continuous wave lasers have output powers from tens of watts to hundreds of kilowatts. Their applications are anywhere localized delivery of high energy is required - manufacturing (welding, cutting, and metal additive manufacturing/3D printing), materials processing and testing, and defense. These same lasers present unique challenges for measuring their properties. Not only is measurement of the delivered laser power important (and challenging) but characterization of the beam quality and the quantifying the coupling of that beam to the material must be addressed. The High-Power Laser Applications Project exists to enhance the ability to measure high-power laser output parameters with the needed accuracy and ease of use appropriate to the application.

Description

Measurement challenges

Traditional measurements of laser power or energy involve absorbing the laser light and measuring the resulting temperature increase of the absorber. However, as the power and total energy delivered by these lasers increases, thermal management, absorber size, and response time begin to limit the effectiveness of traditional measurement approaches. We develop and implement unique measurement approaches to facilitate applications of these high-power lasers.

• Measuring High Laser Powers Using Radiation Pressure: We address the measurement of high laser powers (watts to hundreds of kilowatts) through the ongoing development of a suite of radiation-pressure based power measurement techniques. We measure the laser light’s power without absorbing it. The results are portable high-power instruments capable of long-duration measurements of the world’s highest laser powers with high accuracy and new measurement paradigms.
• Expanding the Limits of Metrology: Radiation-pressure based power metrology opens the opportunity for greatly improved measurement uncertainty through passive amplification of the light’s force signal without commensurate increase in noise. We are developing a High Amplification Laser-pressure Optic (HALO) for a 14x amplification with a 10-kW laser for accuracies better than 0.26 % (k=2) .
• Dynamic Light Absorption: In laser-based manufacturing, laser light delivers energy to heat, cut, melt, sinter, or weld a work piece. In these cases, knowledge of the laser power at the workpiece is not sufficient. The coupling of that laser light into the workpiece is a dynamic process depending on material type, surface finish, and incident power. We have produced high-accuracy data sets describing the dynamic absorptivity during the chaotic laser-metal interaction, permitting software model validation, better understanding of the chaotic processes, and applications for real-time process monitoring.
• Industrial Metrology: In laser powder bed fusion (metal additive manufacturing) the laser power levels are typically between 50 and 1000 W. Power measurements in this range are typically straightforward, but other factors such as calibration period, laser degradation rate, and measurement protocols have practical effects on the accurate delivery of laser power. We are performing a “round-robin” style measurement to assess the real-world performance of laser power delivery to additive manufacturing machines on shop floors, in government laboratories, and within university research facilities.

Our interest is in addressing high-power laser measurements challenges, and we welcome discussions and collaborations.