There are lot, depending on your requirements. Anyway you can try: K~UT@,CS60
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1, Refractive: an achromatic as positive + plano-convex as negative; 4yxf/X)
OR |1OF!(:
2, Reflective: two parabolic mirrors; 'g)5vI~'
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Both of them affer nice spherical aberration performance. {|zQ
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Reminder: compute the laser beam density, ensure you have enough strong optical coating. M#],#o*G
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Good luck.