There are lot, depending on your requirements. Anyway you can try: C]L)nCOBX
%N8I'*u
1, Refractive: an achromatic as positive + plano-convex as negative; ._}}@V_/
OR Af|h*V4Xu
2, Reflective: two parabolic mirrors; {T4_Xn -I
]v
${k
Both of them affer nice spherical aberration performance. ,?GwA@~$k:
t!?`2Z5
Reminder: compute the laser beam density, ensure you have enough strong optical coating. kF|$oBQ
I{IB>j}8
Good luck.