There are lot, depending on your requirements. Anyway you can try: ,
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1, Refractive: an achromatic as positive + plano-convex as negative; e=;@L3f
OR OXX(OCG>
2, Reflective: two parabolic mirrors; j_uY8c>3\q
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Both of them affer nice spherical aberration performance. A|_%'8
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Reminder: compute the laser beam density, ensure you have enough strong optical coating. JvJ!\6Q@
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Good luck.