There are lot, depending on your requirements. Anyway you can try: g@2KnzD
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1, Refractive: an achromatic as positive + plano-convex as negative; R53^3"q~
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2, Reflective: two parabolic mirrors; riZ :#I
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Both of them affer nice spherical aberration performance. $b~[>S-Q
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Reminder: compute the laser beam density, ensure you have enough strong optical coating. iE?yvtr8
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Good luck.