There are lot, depending on your requirements. Anyway you can try: CNU,\>J@$
d7(g=JK<
1, Refractive: an achromatic as positive + plano-convex as negative; R2K{vs
OR W5a7HkM
2, Reflective: two parabolic mirrors; eI99itDQ
^phgNzD
Both of them affer nice spherical aberration performance. d!>.$|b
tAPn? d5
Reminder: compute the laser beam density, ensure you have enough strong optical coating. F{,<6/ayRz
P)D2PVD
Good luck.