There are lot, depending on your requirements. Anyway you can try: J^zi2jtV
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1, Refractive: an achromatic as positive + plano-convex as negative; {fz$Z!8-
OR KIus/S5
RC
2, Reflective: two parabolic mirrors; YfDWM7x7,
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Both of them affer nice spherical aberration performance. Eipp~GD
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Reminder: compute the laser beam density, ensure you have enough strong optical coating. ]U_ec*a
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Good luck.