There are lot, depending on your requirements. Anyway you can try: YdsY2
'lmZ{a6
1, Refractive: an achromatic as positive + plano-convex as negative; x~1.;dBF
OR UrAg*v!Qy
2, Reflective: two parabolic mirrors; },1**_#<Br
MtE18m"z
Both of them affer nice spherical aberration performance. C- 25\
[f`^+,U
Reminder: compute the laser beam density, ensure you have enough strong optical coating. ifA=qn0=}
Qdepzo>E
Good luck.