  We propose a hierarchy set of minimal optical Raman lattice schemes toward
the experimental realization of spin-orbit (SO) couplings of various types for
ultracold atoms, including two-dimensional (2D) Dirac type of $C_4$ symmetry,
2D Rashba and 3D Weyl types. These schemes are well accessible with current
cold-atom technology, and in particular, a long-lived Bose-Einstein
condensation of the 2D Dirac SO coupling has been experimentally proved. The
generation of 2D Rashba and 3D Weyl types has an exquisite request that two
sources of laser beams have distinct frequencies of factor-two difference.
Surprisingly, we find that $^{133}$Cs atoms provide an ideal candidate for the
realization. A common and essential feature is the absence of any fine-tuning
and phase-locking in the realization, and the resulted SO coupled ultracold
atoms have a long lifetime. These schemes essentially improve over the current
experimental accessibility and controllability, and open new experimental
platforms to study high-dimensional SO physics and novel topological phases
with ultracold atoms.
