Asymmetric nano-groove structure two-color surface plasmon beam splitter and beam splitting method

Abstract

The invention discloses a two-color surface plasmon beam splitter with an asymmetric nano-groove structure and a beam splitting method. The two-color surface plasmon beam splitter of the present invention includes: a metal film; a main nano-groove is arranged on the surface of the metal film; an additional nano-groove is arranged on the bottom side of the main nano-groove to form an asymmetric nano-groove Groove structure; by manipulating the relative amplitude and phase difference of the excited SPPs by controlling the depth of the main nanogroove and the additional nanogroove in the structure, the unidirectional excitation of SPPs in one direction is realized at the first working wavelength, and further through Utilizing the contribution of SPPs excited by the third-order waveguide mode, the unidirectional excitation of SPPs in the opposite direction is realized at a shorter second working wavelength. The present invention also has high SPPs excitation efficiency and high extinction ratio and other high performances, and the ultra-small size of hundreds of nanometers is conducive to high integration, so it will be widely used in ultra-high integration SPPs photonic circuits.

Description

technical field [0001] The invention relates to the field of nanophotonics, in particular to a two-color surface plasmon beam splitter based on an asymmetric nano-groove structure and a beam splitting method thereof. Background technique [0002] Surface plasmon polaritons (Surface Plasmon Polaritons) SPPs are currently a hot spot in nanophotonics research. The surface plasmon is a collective oscillation that exists at the interface between the metal and the medium coupled with the light wave and the free electrons in the metal. It is a special electromagnetic field in the interface bound mode. Its existence can be solved by solving the interface between the metal and the medium. It is obtained from Maxwell's equations under the boundary conditions. The biggest feature of SPPs is that they can localize the light field within the sub-wavelength size at the interface between the metal and the medium, breaking through the diffraction limit of traditional optics. At the same ti...

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Problems solved by technology

However, these additional grating structures greatly increase the size of the SPPs beam splitter, which is not conducive to high integration

Furthermore, the beam splitting of SPPs can also be realized by covering a layer of dielectric film with a finite thickness on the asymmetric nanometer single slit, but due to the increase of the dielectric film, the transmission distance of SPPs is shortened, and at the same time, the device design and processing costs are reduced. flexibility

In addition, due to the limitation of the low transmittance of nano-single slits, the efficiency of excitation of SPPs by this kind of two-color surface plasmon beam splitter based on nano-single-slit structure is relatively low, which greatly limits its practical application.

Recently, it was proposed to use the different reflective properties of nanogrooves with different sizes to SPPs, that is, to prepare a pair of parallel nanogrooves with different widths to realize submicron beam splitters, but the beam splitting ratio is too low. Only beam splitting ratios of 3:1 and 1:2 are obtained at 650nm and 750nm respectively

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