There are lot, depending on your requirements. Anyway you can try: I{0k
[(LV
1, Refractive: an achromatic as positive + plano-convex as negative; i?;r7>
OR jLg@FDb~
2, Reflective: two parabolic mirrors; ["<nq`~
92W&x'
Both of them affer nice spherical aberration performance. aiCFH_H4;L
V%
TH7@y
Reminder: compute the laser beam density, ensure you have enough strong optical coating. e=P
8Q`WB0E<|
Good luck.