Active unidirectional propagation of surface plasmons at subwavelength slits

Abstract

Highly efficient, active and compact, unidirectional surface plasmon (SP) propagator composed of double subwavelength slits; filled with organic electro-optic (EO) material is proposed and investigated. By selecting appropriate structure parameters, obtained by solving phase relations between slits, the relative phase of SP generated at the slit exit aperture can be tailored. Simulation results show under normal illumination and external voltage of 8.7 V, SP launching efficiency of 55% and unidirectional SP extinction ratio about 47dB at wavelength of 632.8 nm is achieved. The power consumption of the structure is on the order of 9 fJ/bit which meet the power consumption limitation for optical devices. Moreover, the structure is very compact with effective total length of 1.2 µm and thickness of 0.6 µm.

Broadband and efficient plasmonic control in the near-infrared and visible via strong interference of surface plasmon polaritons

“…Additionally, for near-infrared frequencies, where excitation of quasi-cylindrical waves (CWs) may dominate [12], we demonstrate that their contribution to the total electromagnetic fields is suppressed considerably in the nanoslit pair, as they only interfere weakly in comparison to the SPPs. In this respect, the proposed scheme addresses spectral control to circumvent electromagnetic dispersion effects in the nearinfrared, an issue that remains inadequately tackled in other similar doublet geometries proposed for the directional launching of SPPs [7,13]. Another aspect uncovered in this study is that, compared to the single slit device (such as in Refs.…”

Thermally Controllable High-Efficiency Unidirectional Coupling in a Double-Slit Structure Filled With Phase Change Material

“…Therefore narrow slits yield in large effective refractive indexes. The values of N eff for our desired parameters are obtained from our previously reported result [18]. Therefore, by changing the slit width or dielectric medium inside the slits, different phase retardation can be imposed on travelling SPPs through the slit.…”

“…Numerous electrically and all optically controlled schemes by exploiting the electro-optical effect have been proposed, characterized, and fabricated [15]- [17]. Previously, we introduced an active unidirectional launcher based on a double-slit structure that yields directional propagation at the desired direction with 55% coupling efficiency and extinction ratio of 1:70 under external voltage [18]. However, the fabrication process for electro-optical materials remains a major challenge.…”

Theoretical analysis of plasmonic unidirectional propagation at visible frequency based on subwavelength waveguide

“…Conventionally, by adding periodical gratings to only one side of the metal film, SPPs can be unidirectionally launched to the other side due to the Bragg reflection of the periodical structures [19,20]. In addition, two subwavelength slits or cavities are also employed to obtain the unidirectional SPPs generations according to the SPPs interference effect [21][22][23]. The most concerns on these devices are the launching efficiency at the desired direction and the isolation at the opposite direction.…”