There are lot, depending on your requirements. Anyway you can try: SoX\S|}%6[
v7x%V%K
1, Refractive: an achromatic as positive + plano-convex as negative;
,83%18b
OR UfcQFT{()
2, Reflective: two parabolic mirrors; Hd
H,
(D5 dN\
Both of them affer nice spherical aberration performance. H&`0I$8m
2fIHFo\8
Reminder: compute the laser beam density, ensure you have enough strong optical coating. : p# 5nYi
#!="b8F
Good luck.