There are lot, depending on your requirements. Anyway you can try: u'? +JUd1
'7oR|I
1, Refractive: an achromatic as positive + plano-convex as negative; I{w(`[Nxw*
OR 1{/Cr K/o
2, Reflective: two parabolic mirrors; [%^0L~:
Wm1dFf.>
Both of them affer nice spherical aberration performance. 'LoWp} f9
2lfEJw($
Reminder: compute the laser beam density, ensure you have enough strong optical coating. f5//?ek
~AWn 1vFc
Good luck.