Measurement of the laser beam quality using knife-edge method

Abstract

The parameter of laser beam is to evaluate the characteristics of the laser beam from quality. Laser beam analysis apparatus in this paper is use knife-edge method to get the laser beam quality. This machine move knife-edge line with laser beam cross section, which on the mechanical platform. Light detector measure the transmission power of laser beam. The sensor's analog signal input the A /D converter, then change digital corresponding signals. The instrument's measure system can calculated the parameter of the laser beam though the power and the position of the power that be measured. The knife-edge in the measure system must be sure has good quality, thinning enough, and must be perpendicular to the direction of the axis laser beam, or it will impact on measurement accuracy. During the measure process, in order to decrease the measurement error we must carefully rotating micrometer screw device. It mainly because the response speeds of light detector and A/D converter is not fast enough. In waist position, laser power density is relatively high, so the situation should be based on the actual choice of laser power to prevent the knife-edge will not burn. At last using the MATLAB to carry out the simulation analysis, the method is proved that it can accurately recover the complicated energy distribution, and the system is proved that it can improve the measurement accuracy effectively and can get parameter of laser beam goodly. Key words: knife-edge method, laser beam quality, MATLAB, energy distribution, laser beam analysis apparatus, natural density filter