Abstract
Beam splitters, especially those with tunable split ratios, play significant role in interferometers, spectrometers, and communication systems. To this end, we proposed a polarization-controllable beam splitter based on dielectric metasurface composed of an array of dielectric pillars. The dielectric metasurface presents phase gradients along two orthogonal directions, say, x- and y- axis, with each phase gradient applicable to one of two orthogonal linear polarizations. Due to the orthogonality of the dual phase gradients in both position and polarization, an elliptically polarized incident beam can be diffracted into two refracted beams, one lies within xoz plane and the other in yoz plane. More importantly, the split ratio of the two refracted beams is continuously tunable by changing the ellipticity of incident beam. Under extreme case, x- or y- polarized incident beam is refracted into one beam, but in different planes for different kind of linear polarization. Besides, the refracted angle of each refracted beam in respective refracted plane can be easily set by adjusting the phase difference of adjacent rows or columns of metasurface. With same method, a polarization-controllable dual-wavelength beam splitter is also achieved on the basis of phase-gradient metasurface. Such a noncoplanar beam splitter with tunable split ratios may play significant role in novel miniature optical devices and systems.
Highlights
A beam splitter is an essential component in various optical and photonic applications for separating lights with different polarizations, wavelengths, and powers [1]–[5]
We proposed a polarization-controllable beam splitter based on dielectric metasurface composed of an array of dielectric pillars
The reflection-type design can reduce the loss to some extent, the intrinsic heat dissipation is still a stumbling block to high efficiency of the plasmonic metasurface
Summary
A beam splitter is an essential component in various optical and photonic applications for separating lights with different polarizations, wavelengths, and powers [1]–[5]. The reflection-type design can reduce the loss to some extent, the intrinsic heat dissipation is still a stumbling block to high efficiency of the plasmonic metasurface This limitation can be overcome by replacing metals with all-dielectric structures [25], [26]. The split ratio is tuned by shifting the relative position between the center of incident beam and the center of the metasurface This kind of beam splitter may not be applicable to miniaturized optical instruments and systems where all devices are spatially unmovable. Since the supercell can be designed at a specific wavelength, the noncoplanar beam splitter can be designed as a polarization-controllable dual-wavelength beam splitter We envision that this type of noncoplanar beam splitters with tunable split ratios have significant applications in complex miniaturized optical devices and systems
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