There are lot, depending on your requirements. Anyway you can try: BoJYP
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1, Refractive: an achromatic as positive + plano-convex as negative; {s=n "*Qp)
OR ,QDS_u$xi&
2, Reflective: two parabolic mirrors; AOT +4*)%
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Both of them affer nice spherical aberration performance. .T*K4m{b0
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Reminder: compute the laser beam density, ensure you have enough strong optical coating. Who7{|M\'
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Good luck.