There are lot, depending on your requirements. Anyway you can try: hOj{y2sc
'}.Yf_
1, Refractive: an achromatic as positive + plano-convex as negative; .biq)Le
OR iGyetFqKw
2, Reflective: two parabolic mirrors; hG1:E:}
*8}b&4O~
Both of them affer nice spherical aberration performance. =nEP:7~{
Ln+l'&_nb
Reminder: compute the laser beam density, ensure you have enough strong optical coating. B8@mL-Z-;
M(-)\~9T
Good luck.