(a) The schematic diagrams of radiation forces acting on a CQWN confined in the z direction, where F_x and F_z denote the x and z components of the radiation force induced by a monochromatic plane wave with p- or s-polarized state, respectively. (b) The schematic diagrams of the CQWN, where L_L, L_B, and L_R denote the left well, mid-barrier, and right well widths, V₁ and V₂ denote the mid-barrier and outer barrier height, respectively. The signs ↑ and ⊙ denote polarization direction of p- and s-polarized light waves, respectively.