There are lot, depending on your requirements. Anyway you can try: "4riSxEyF
C8Qa$._
1, Refractive: an achromatic as positive + plano-convex as negative; /aZ+T5O
OR zgNc4B
2, Reflective: two parabolic mirrors; a
yCY~=i
JBE!j-F
Both of them affer nice spherical aberration performance. }<@b=_>S
oSyyd
Reminder: compute the laser beam density, ensure you have enough strong optical coating. 1FlX'[vh
bwD,YC
Good luck.