(Color online) Atomic excitation probability as function of Γ t with a = 2 b . (a) The transition frequency ω A = ( Ω 11 + Ω 31 ) / 2 . The atom is located at three different positions z 0 = 0 (black dot-dashed line), z 0 = λ 1 A / 8 (blue solid line), z 0 = λ 1 A / 4 (red dashed line). (b) The transition frequency ω A = ( Ω 31 + Ω 51 ) / 2 . The atom is located at z 0 = λ 1 A / 4 . The red dashed line presents the contribution of the TM₁₁ mode. The blue solid line gives the contribution of both TM₁₁ and TM₃₁ modes.