There are lot, depending on your requirements. Anyway you can try: ZLc -RM
RW|`nL
1, Refractive: an achromatic as positive + plano-convex as negative; 'g6\CZw(#
OR ng[Ar`
2, Reflective: two parabolic mirrors; [O$Wa:< 0x
.I$qCb|FP
Both of them affer nice spherical aberration performance. C'G/AU
!6n_}I-W
Reminder: compute the laser beam density, ensure you have enough strong optical coating. z[LNf.)}
R}'bP
Good luck.