There are lot, depending on your requirements. Anyway you can try: l1??b
B?M+`;
1, Refractive: an achromatic as positive + plano-convex as negative; +EB##
OR oK>,MdB
2, Reflective: two parabolic mirrors; 7~16letQ
TQou.'+v
Both of them affer nice spherical aberration performance. g DhwJks
9NT;^K^I
Reminder: compute the laser beam density, ensure you have enough strong optical coating. MXy{]o_H~
%L/=heBBd
Good luck.