There are lot, depending on your requirements. Anyway you can try: g^7zDU&'
yE(<F2
1, Refractive: an achromatic as positive + plano-convex as negative; Z^=(9:
OR a .?AniB0
2, Reflective: two parabolic mirrors; [:qJ1^U U
LC$M_Cpw
Both of them affer nice spherical aberration performance. V?mk*CU
?$uEN_1O\@
Reminder: compute the laser beam density, ensure you have enough strong optical coating. +XW1,ly~
S)W?W}*R\
Good luck.