There are lot, depending on your requirements. Anyway you can try: !;SpQ28
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1, Refractive: an achromatic as positive + plano-convex as negative; 8ycmvpJ
OR {__Z\D2I
2, Reflective: two parabolic mirrors; -R!qDA"
W|U!kqU
Both of them affer nice spherical aberration performance. 0Fw0#eE
Co2* -[R
Reminder: compute the laser beam density, ensure you have enough strong optical coating. dqMR<Nl&
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Good luck.