There are lot, depending on your requirements. Anyway you can try: 6Zq7O\
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1, Refractive: an achromatic as positive + plano-convex as negative; wRQMuFGY
OR e&F=w`F\
2, Reflective: two parabolic mirrors; w(R+p/RF
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Both of them affer nice spherical aberration performance. #|acRZ9
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Reminder: compute the laser beam density, ensure you have enough strong optical coating. O*hQP*Rs
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Good luck.