There are lot, depending on your requirements. Anyway you can try: yw1Xxwc
}g:'K
1, Refractive: an achromatic as positive + plano-convex as negative; y.(m#&T
OR U/xzl4m6
2, Reflective: two parabolic mirrors; :Y4Sdj
Mky^X,r
Both of them affer nice spherical aberration performance. H}(WL+7
+>yspOEz
Reminder: compute the laser beam density, ensure you have enough strong optical coating. Hr T@Df
'pF$6n;
Good luck.