There are lot, depending on your requirements. Anyway you can try: QqU>V0y"w(
4UV<Q*B\F
1, Refractive: an achromatic as positive + plano-convex as negative; p3R: 3E6p
OR 5B76D12
2, Reflective: two parabolic mirrors; ,2C{X+t
(yB)rBh>n
Both of them affer nice spherical aberration performance. g!*5@k|C
U'K{>"~1a
Reminder: compute the laser beam density, ensure you have enough strong optical coating. Z2cumx(
]#*S. r]
Good luck.