There are lot, depending on your requirements. Anyway you can try: P1b5=/}:V
6mJa
1, Refractive: an achromatic as positive + plano-convex as negative; y K~;LV
OR /O1r=lv3Z
2, Reflective: two parabolic mirrors; #Al.Itj
W8Z&J18AU
Both of them affer nice spherical aberration performance. m$xL#omD
}vkrWy^
Reminder: compute the laser beam density, ensure you have enough strong optical coating. vu[+UF\G
7z'l}*FRD
Good luck.