There are lot, depending on your requirements. Anyway you can try: !(Y|Vm'
!7#*Wdt+P
1, Refractive: an achromatic as positive + plano-convex as negative; p\'X%R
OR RmKbnS$*q
2, Reflective: two parabolic mirrors; a>8]+@
t,XbF
Both of them affer nice spherical aberration performance. ^56D)A=
d9e~><bPJ
Reminder: compute the laser beam density, ensure you have enough strong optical coating. G;t<dJ8
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Good luck.