Efficient and wavelength-dependent directional launching of a nondiffracting surface plasmon polariton beam device

The high-efficiency excitation and dynamic manipulation of the nondiffracting surface plasmon polariton (SPP) beam are important prerequisites for practical applications including the next-generation on-chip devices, near field optical trapping, and micromanipulation. Here we proposed two kinds of high-efficiency coupling and wavelength-dependent nondiffracting SPP beam unidirectional devices, which can generate and manipulate Bessel-like SPP beam or SPP Bottle beam, respectively. Different from the conventional groove or ridge structure that equally split SPP power to propagate from the boundary to both sides, the compact coupling element directs all of the SPP power of the matched wavelength to one side, resulting in higher collecting efficiency. Besides, as the wavelength of the incident light is changed, the generated Bessel-like SPP beam or SPP Bottle beam can be directionally excited on one side of the device. The design of the proposed devices provides a new means for constructing plasmonic devices with wavelength-dependent dynamic manipulation of nondiffracting SPP beams and has potential applications in on-chip interconnect circuits and near-field optical trapping.