There are lot, depending on your requirements. Anyway you can try: =>ooB/
,|?-\?I
1, Refractive: an achromatic as positive + plano-convex as negative; |CME:;{T
OR *wW/nr=\;
2, Reflective: two parabolic mirrors; u@SE)qg
$M\[^g(q
Both of them affer nice spherical aberration performance. 5TlPs_o
ZoJ:4uo
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Reminder: compute the laser beam density, ensure you have enough strong optical coating. F^kH"u[
mk JS_6
Good luck.