Objective High-power lasers have important applications in industrial processing, military defense, scientific research, and other fields. With the development of laser technology in recent years, the output power level of lasers has been continuously improved. The accurate measurement of power is the basis of researches and applications of high-power lasers. Traditional high-power laser measurement mainly uses calorimetric methods. The device is large and heavy, and the surface of the absorption material is easily damaged by laser.
Methods Although the photon has no static mass, it has momentum. When the laser is irradiated on the surface of the object, pressure will be generated. Using the light pressure effect, the laser power can be traced directly to the micro-nano force or micro-mass. Figure 1 is the principle diagram of the measuring device, which adopts the structural design of three mirrors, and the transmission direction of the laser remains unchanged after three reflections. One of the mirrors is installed on the weighing module, and the weighing module is placed horizontally in the same manner as the mass calibration.
Results and Discusions Figure 2 shows the time response curve of the optical pressure measurement device. The laser emission time is set to 20 s, and the response time of the measurement device is only 3 s. A calorimetric laser power meter that has been accurately calibrated is placed behind the optical pressure measurement device for simultaneous measurement. The measurement results of the two methods are compared. The maximum relative deviation is less than 1%. Limited by the output power of the test light source, the upper limit of power measurement is only verified to 15 kW. In fact, the upper limit of power measurement of the device is only limited by the damage threshold of the laser mirror, so the upper limit of power measurement can reach 100 kW or even higher.
Conclusions Based on the principle of light pressure, a set of high-power laser measurement devices is established, and the power measurement uncertainty is better than 2% (confidence factor k is 2). The light pressure method is compared with the calorimetric method in the power range of 0.6--15 kW, and the maximum relative deviation is less than 1%. At the same time, the measurement device has the advantages of fast response speed, high measurement accuracy, and online measurement.
