There are lot, depending on your requirements. Anyway you can try: 1v.c 6~
+BETF;0D
1, Refractive: an achromatic as positive + plano-convex as negative; oX30VfT
OR ,!#*GZ.ix
2, Reflective: two parabolic mirrors; 2mVD_ s[`
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Both of them affer nice spherical aberration performance. M2OIBH4!
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Reminder: compute the laser beam density, ensure you have enough strong optical coating. PgtJ3oq[}
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Good luck.