There are lot, depending on your requirements. Anyway you can try: Icx)+Mq
wS [k}
1, Refractive: an achromatic as positive + plano-convex as negative; >}r
1A
OR XvZ5Q
2, Reflective: two parabolic mirrors; @2eH;?uO
?{~. }Vn
Both of them affer nice spherical aberration performance. {~V_6wY g
PI)uBA;
Reminder: compute the laser beam density, ensure you have enough strong optical coating. C9j5Pd5q1L
zX8{(
Good luck.