In order to achieve the uniform picosecond laser micro-machining effect, this study carries out the research of shaping the original incident Gaussian beam into a micron-level flat-top beam at the focal position. Based on the principle of diffractive optics, the phase distribution of the shaping element is calculated which meets the micron-level flat-top beam output requirements and the verification of the shaping effect after transforming through the phase distribution is simulated. When the simulated output beam distribution meets the design requirements, the shaping elements is manufactured. Finally, the shaping element is used in a picosecond laser micro-scribing experiment and the scribing effect is analyzed. The final experimental results show that the picosecond laser micro-scribing test is carried out with the shaped flat-top beam, and the uniform scribing effect is obtained which satisfies the design requirements.
In this paper, a 15-direction ring laser diode array is chosen as pumping source in order to get uniform pump in laser medium. The diameter of laser rod is 15mm for obtaining high output laser energy. A numerical model of the side-pump pulsed Nd:YAG laser amplifier is set up. The finite element method using Ansys software is adopted to analyze the time-varying thermal effect. In order to find the temperature influence of the pump light’s distribution, the temperature distributions in laser rod loaded by 15-direction Gaussian beam and simplified uniform beam are calculated and the results are comparatively analyzed. Despite the highest temperature in laser rod is different, the whole variation trend is similar which indicates time-varying characteristic. The thermal lens effect is also calculated and the results indicate that the temperature gradient in the medium plays the most important role. This study could provide a simulation tool to evaluate the thermal effect of the laser amplifier.