There are lot, depending on your requirements. Anyway you can try: G=Bj1ss.
RM$S|y{L
1, Refractive: an achromatic as positive + plano-convex as negative; <)rH8]V
OR W7>_nK+g?
2, Reflective: two parabolic mirrors; `P*j~ZLlXN
iAhRlQ{Qu
Both of them affer nice spherical aberration performance. 1H@F>}DP
3e1"5~?'<
Reminder: compute the laser beam density, ensure you have enough strong optical coating. KO$8lMm$
1uzfV)
Good luck.