There are lot, depending on your requirements. Anyway you can try: YRQ?:a{H
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1, Refractive: an achromatic as positive + plano-convex as negative; r4Xaa<
OR {01^xn.
2, Reflective: two parabolic mirrors; b%7zu}F
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Both of them affer nice spherical aberration performance. M[cAfu
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Reminder: compute the laser beam density, ensure you have enough strong optical coating. iUq_vQ@}}
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Good luck.