Ruy Lopez

When doing the Ruy Lopez after black does 3...a6 should white then go 4.Bxc6 bxc6 5. Nxe5 and get a pawn advantage or retreat the bishop like 4. Ba4 b5 5. Bb3 or is there some other way to get a bigger advantage than the one pawn when you take the knight? Please comment because I really need some help with this