Design of laser collimating and focusing system under small working distance

摘要

Laser micro thruster based on semiconductor laser has great advantages in volume. However, the design of opticalcollimating and focusing system is very challenging under highly integrated conditions. The operating distance from thelaser exit to the working ablation target needs to be tens of millimeters. Based on the ray tracing method, a convenientand fast design method of the optical collimating and focusing system is proposed under the small working distance. Themethod is verified by an example. The design conditions are as follows: laser wavelength is 940 nm, fiber core diameteris 105 microns, and the numerical aperture is 0.22; focusing spot diameter is 50 microns; fiber head and ablation surfacedistance is not more than 20 mm; only one lens is used. Using the method proposed in this paper, the final design resultsare as follows: doubly convex lens R_1 = 5mm, R_2 = 25mm～30mm, lens aperture D = 6mm, central thickness T_C = 2mm.According to the energy simulation results, the method proposed in this paper is effective.