There are lot, depending on your requirements. Anyway you can try: _0(Bx?[h
V8{5 y
<Y>
1, Refractive: an achromatic as positive + plano-convex as negative; sM$gfFx
OR +Pm
yFJH
2, Reflective: two parabolic mirrors; R#UcwX}o
0755;26Bx
Both of them affer nice spherical aberration performance. }D>nXhO&
1JXa/f+
Reminder: compute the laser beam density, ensure you have enough strong optical coating. *iVCHQ~
m}dO\;
Good luck.