There are lot, depending on your requirements. Anyway you can try: ~g96o81V
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1, Refractive: an achromatic as positive + plano-convex as negative; 0eaUorm)
OR Oylp:_<aT
2, Reflective: two parabolic mirrors; pgfu+K7?w
<VgE39 [
Both of them affer nice spherical aberration performance. I1J)#p%H.
8I {56$
Reminder: compute the laser beam density, ensure you have enough strong optical coating. :6sGX p
S&`O\!NF
Good luck.