There are lot, depending on your requirements. Anyway you can try: m", $M>
b6oPnP_3P
1, Refractive: an achromatic as positive + plano-convex as negative; UAH} ])U
OR Fc42TH
p
2, Reflective: two parabolic mirrors; }^P( p?~
1
!OQxY}f
Both of them affer nice spherical aberration performance. Gl}=Q7
RQ9T<t42
Reminder: compute the laser beam density, ensure you have enough strong optical coating. J%D'Xlb
O,: en t|
Good luck.