There are lot, depending on your requirements. Anyway you can try: [ v*ju!
20Wg=p9L
1, Refractive: an achromatic as positive + plano-convex as negative; {3aua:q
OR 5$C-9
2, Reflective: two parabolic mirrors; <7jW_R@
~b8]H|<'Y
Both of them affer nice spherical aberration performance. pFjK}JOF
Er?&Y,o
Reminder: compute the laser beam density, ensure you have enough strong optical coating. ?&1!vz
)+9Uoe~6
Good luck.