There are lot, depending on your requirements. Anyway you can try: <\d`}A:&
1vh[sKv9%
1, Refractive: an achromatic as positive + plano-convex as negative; eOb)uIF
OR N7q6pBA"E
2, Reflective: two parabolic mirrors; on7?V<
F)aF.'$-/
Both of them affer nice spherical aberration performance. ?wIw$p>wT
aMK\&yZD
Reminder: compute the laser beam density, ensure you have enough strong optical coating. A0ZU #"'/
%xXb5aY
Good luck.