There are lot, depending on your requirements. Anyway you can try: m$nT#@l5bH
["4sCB@Tr
1, Refractive: an achromatic as positive + plano-convex as negative; JkT, i_
OR EC[2rROn\
2, Reflective: two parabolic mirrors; Z"spua5
@C[]o.r
Both of them affer nice spherical aberration performance. Rou$`<{H
sg@)IEg</v
Reminder: compute the laser beam density, ensure you have enough strong optical coating. aLr\Uq,83
QLNQE 6-
Good luck.