There are lot, depending on your requirements. Anyway you can try: e}W)LPR!
FGkVqZ Y2?
1, Refractive: an achromatic as positive + plano-convex as negative; 4&iCht
=
OR }GIt!PG
2, Reflective: two parabolic mirrors; D/' dTrR
S|}L &A
Both of them affer nice spherical aberration performance. d"Y{UE
c*M}N?|6
Reminder: compute the laser beam density, ensure you have enough strong optical coating. Bbp|!+KP{(
P'rb%W
Good luck.