There are lot, depending on your requirements. Anyway you can try: !W{|7Es?.
@N1ta-D#
1, Refractive: an achromatic as positive + plano-convex as negative; 9{?<.%
OR bP(V#6IJ8
2, Reflective: two parabolic mirrors; oI/@w
`Nc3I\tCM
Both of them affer nice spherical aberration performance. Dbz\8gmY
0XvMaQXQF
Reminder: compute the laser beam density, ensure you have enough strong optical coating. 2lE {
P
BDD^*Y
Good luck.