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We propose a new scheme on unidirectional surface plasmon-polariton (SPP) excitation with the following advantages: ultracompact size, working at arbitrary incidence angle and over a wide spectrum. The proposed structure utilizes a partially filled metallic slot with dielectric to realize unidirectional SPP excitation via direct field manipulation. We theoretically and numerically show that unidirectional SPP excitation with a ratio of 93% can be achieved by a structure with a 50 nm slot. The proposed structure keeps its functional capability over incident angles from -80° to 80°, and has a broadband working spectrum of more than 70 nm.

Janus transition-metal dichalcogenides (JTMDs) with an asymmetric structure have attracted much attention because of their obvious potential in electronic and optical applications. However, there are few research studies on field-effect transistors (FETs) related to JTMDs, and the inherent device transport performance is unclear so far. In this work, we systematically investigate the ballistic transport performance of sub-10 nm monolayer Janus MoSSe and WSSe metal oxide semiconductor FETs (MOSFETs) based on ab initio quantum transport simulations. The on-state current, delay time, and power dissipation of Janus MoSSe and WSSe MOSFETs with a proper doping concentration under the requirements of high performance (HP) in the International Technology Roadmap for Semiconductor are systematically studied. The calculated results indicate that the on-state currents of MoSSe MOSFETs can satisfy about 35% requirement of HP standards and the WSSe MOSFETs fulfill the HP application targets until the gate length is scaled down to 4 nm. In addition, we discussed the underlying physical mechanisms and further explored the effect of channel material oxidation on the device performance. As a result, it is believed that our predictions could greatly stimulate the potential of Janus MoSSe and WSSe applied to transistors.

A new structure to be used as a tunable unidirectional surface plasmon source is introduced. The structure is composed of two silver films, with a nanoslit fabricated in the top Ag film and lying below is a movable Ag film. The field distribution of the structure is investigated by using the finite-difference time-domain(FDTD) method. It is found that the surface plasmon polariton intensity and the splitting ratio change periodically as the bottom film is moved, which is interpreted in terms of surface plasmon polaritons interference in two Fabry-Perot(F-P) cavities. The period obtained by the FDTD agrees well with the F-P interferometer model. The surface plasmon polaritons can be unidirectionally excited with a large intensity splitting ratio.

Discrete plasmonic Talbot effect in the subwavelength metal waveguide arrays (SMWAS) is theoretically analyzed and numerically simulated. Based on the finite-difference time-domain technique, we discuss the influence of the structural parameters on the Talbot distance. By carefully choosing the geometry parameters, the Talbot distance decreases to about one third of the incident wavelength. The numerical simulation results agree with the theory of the discrete Talbot effect in the SMWAS.