There are lot, depending on your requirements. Anyway you can try: ${e&A^h
M1uP\Sa
1, Refractive: an achromatic as positive + plano-convex as negative; YY!!<2_
OR deM~[1e[
2, Reflective: two parabolic mirrors; %vc'{`P
nO@+s
F
Both of them affer nice spherical aberration performance. <R~KM=rL
*tAqt2{48
Reminder: compute the laser beam density, ensure you have enough strong optical coating. FT_k^CC
apaIJ+^[
Good luck.