Abstract: The aberration is produced and the processing result is affected for the refractive index difference between the processed material and air in laser micro-fabrication. The aberration expressions are derived and the curves of optical system parameters, working depth and aberration are obtained by wave-front aberration function based on laser microfabrication mechanism. Zernike polynomials cycle is used to compensate for the aberrations to obtain post-compensation system point spread function. Take it for example, the femtosecond laser pulses is used for machining points in two-photon photo-chromic materials, a numerical simulation is conducted for the compensation function. Simulation results show that the aberration can be corrected effectively by the established model of compensation. When the primary aberration is compensated, the attenuation of the fluorescence signal intensity at the processing points has been significantly improved and the working depth is close to 600 μm. After secondary aberration compensation, the signal intensity does not change as the working depth is changed. Kepler telescope system is proposed to be used for aberration compensation and the compensation effect is analyzed based on the experiments. Theoretical and experimental results provide a sufficient basis for reducing the aberrations in laser microfabrication process and improving processing effects.

Key words: micro-fabrication;femtosecond laser;refractive index;Zernike polynomials;aberration compensation