Accurate power measurement is the basis of high-power laser applications, and ensuring the quality of laser-processed products is crucial. Owing to the progress in fiber-laser technology, the maximum output power afforded by industrial-grade fiber lasers has increased continually. A set of ultrahigh-power laser-measurement devices based on the principle of light pressure was established to measure the output power of a 200 kW industrial-grade fiber laser.

In this study, a focused laser beam was incident at a small angle to a light-pressure power meter (LPPM) after being output from the lens set; furthermore, it was absorbed by the laser dump after being output from the LPPM, as shown in Fig. 1. The LPPM was equipped with three ultrahigh-reflectance, high-damage-threshold mirrors, whose reflectance exceeds 99.995% in the 950?1100 nm waveband. Two rectangular mirrors were mounted on the top of the LPPM at an angle of 110°, and another 90-mm-diameter mirror was connected to the weighing module.

We performed power measurements at different levels, as shown in Fig. 2(a). The measurement repeatability is better than 0.1% (calculated using the polar deviation method), and the response time of 0%?100% power is less than 3 s. The full-power output is 200.50 kW, with a response time of 2.6 s, as shown in Fig. 2(b). The measurement uncertainty of the laser power was evaluated and calculated based on the guide to the uncertainty in measurement (GUM) and the Monte Carlo method (MCM), as shown in Fig. 3. The rapid decrease in the measurement uncertainty in the power range of 3?10 kW is primarily caused by the gradual decrease in the contributions of the mass-measurement uncertainty component and resolving power to the measurement uncertainty as the measured power increases. When the laser power exceeds 10 kW, the variation in the measurement uncertainty stabilizes and is better than 0.76% (confidence factor k = 2).

We report the power for industrial-grade fiber lasers measured by an LPPM. This LPPM realizes highly accurate laser power measurements traceable to the Système International (SI) basic unit (kg).