There are lot, depending on your requirements. Anyway you can try: .p%V]Ka
o.wXaS8
1, Refractive: an achromatic as positive + plano-convex as negative; \_ MWZRMc5
OR r=# v@]zB
2, Reflective: two parabolic mirrors; K0Lc~n/
#g~]2x
Both of them affer nice spherical aberration performance. VVqpzDoXG
Ymm*p,`
Reminder: compute the laser beam density, ensure you have enough strong optical coating. LBIEG_/m
0s6eF+bs
Good luck.