There are lot, depending on your requirements. Anyway you can try: [Ufx=BPx3
kO/]mNLG
1, Refractive: an achromatic as positive + plano-convex as negative; '
o(7@
OR U^
;H{S
2, Reflective: two parabolic mirrors; ;Q\MH t*
V)jF]u~g
Both of them affer nice spherical aberration performance. Ng|c13A=
J. $U_k
Reminder: compute the laser beam density, ensure you have enough strong optical coating. Xv2Q8-}w
+<rWYF(ii/
Good luck.