There are lot, depending on your requirements. Anyway you can try: `x~k}
k7>* fQ89@
1, Refractive: an achromatic as positive + plano-convex as negative; 99G/(Z}
OR fW!~*Q
2, Reflective: two parabolic mirrors; y&t&'l/m
\r^=W=
Both of them affer nice spherical aberration performance. P9:7_Vc
hUSr1jlA
Reminder: compute the laser beam density, ensure you have enough strong optical coating. #p&iH9c_
RZjTUMAz4
Good luck.