There are lot, depending on your requirements. Anyway you can try: |vnfY;
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1, Refractive: an achromatic as positive + plano-convex as negative; v:<UbuJw
OR zRJopcE<
2, Reflective: two parabolic mirrors; >i4UU0m
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Both of them affer nice spherical aberration performance. a-,BBM 8|
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Reminder: compute the laser beam density, ensure you have enough strong optical coating. $IQ !g
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Good luck.