There are lot, depending on your requirements. Anyway you can try: or]kXefG3
E]j2%}6Z%
1, Refractive: an achromatic as positive + plano-convex as negative; 7Q3a0`Iq
OR *&lNzz5&
2, Reflective: two parabolic mirrors; LHJjPf)F
6l-V%3-
Both of them affer nice spherical aberration performance. CP!>V:w%9!
BX=YS)
Reminder: compute the laser beam density, ensure you have enough strong optical coating. T`.RP&2/d
o>}fKg<
Good luck.