There are lot, depending on your requirements. Anyway you can try: tW"s^r=95
@zSj&4
1, Refractive: an achromatic as positive + plano-convex as negative; \_AoG8B
OR ]`TX%Qni
2, Reflective: two parabolic mirrors; X{;5jnpG
u~\ NL{
Both of them affer nice spherical aberration performance. T)*tCp]
V*1-wg5>
Reminder: compute the laser beam density, ensure you have enough strong optical coating. 9 N9Q#o$!.
JJu}Ed_
Good luck.