We propose axial line-focused spiral zone plates (ALFSZPs) for generating tightly focused X-ray vortex beams with ultra-long depth of focus (DOF) along the propagation direction. In this typical design, compared with the conventional spiral zone plates (S
Terahertz (THz) wave transmission through a thin metal film with periodic arrays of subwavelength rectangular holes is investigated systematically. The roles of the waveguide resonances and surface plasmon polaritons (SPPs) in extraordinary transmission a
We propose a scheme to prepare the Bell states for atomic qubits trapped in separate optical cavities via atom-cavity-laser interaction. The quantum information of each qubit is encoded on the degenerate ground states of the atom, so the entanglement betw