There are lot, depending on your requirements. Anyway you can try: 7!@-*/|!S9
cii_U=
1, Refractive: an achromatic as positive + plano-convex as negative; w~(1%p/
OR Wvbf"hq
2, Reflective: two parabolic mirrors; *w^C"^*
S^-DK~Xt4
Both of them affer nice spherical aberration performance. x2OaPlG,&V
"'c
A2~
Reminder: compute the laser beam density, ensure you have enough strong optical coating. RN$1bxY
zMj#KA1
Good luck.