Far-Infrared Circular Polarization and Polarization Filtering Based on Fermat's Spiral Chiral Metamaterial

Abstract

A bilayered-twisted Fermat's spiral chiral metamaterial (FSCMM) is proposed for the realization of circular polarization of far-infrared waves and polarization filters. It is demonstrated through full-wave simulations that the proposed FSCMM can convert waves from linear to circular polarization (CP) around 2.5 THz. The reported FSCMM is sensitive to the handedness of circularly polarized light, where it can filter out either righthanded or left-handed CP light with an optical isolation of 35 dB around 2.5 THz. The proposed FSCMM is compact with a dimension of =4 Â =4 Â =9 at the far-infrared operating waveband. The CP conversion and filtering functionalities of the proposed FSCMM are ensured for oblique incidences up to 20 with an optical isolation of more than 25 dB for both x -and y -oriented linear polarized excitations. The operation bandwidth of the proposed system is enhanced in the level of 0.058 THz to 0.11 THz for twoand three-unit-cell composite systems, respectively. Due to the strong circular dichroism, compactness, wide-angle functionalities, and appreciable bandwidth, the proposed FSCMM is useful for the development of integrated far-infrared spectroscopic and imaging devices.

Polarization conversion based on plasmonic phase control by an ultra-thin metallic nano-strips

“…Taking this parameter, the feature polarized angel θ 0 = 42.29 • and energy transmissivity T =0.46 can be calculated by the formula (4) and (5) under the conditionẼ x | = Ẽ y , and T is higher than the transmissivity of some analogous metamaterial devices. 5 In this sample, the right red triangle corresponds to an incident infrared wavelength between 900nm-1000nm, and the transmission coefficient of x polarization is smaller which led to extremely low energy transmissivity, of no use value over this. To obtain the optimum structure parameters of ultra-thin metallic nano-strips based quarterwave plate for a feature wavelength needed, we have to calculate and analyze the relationship of the phase difference of transmissions and the transmission coefficients to nano-strips period and incident wavelengths.…”

“…Meta-materials/meta-surfaces has the excellent ability of optical control and some achievements have been gained by utilizing Meta-material/meta-surfaces to make polarization conversion devices. [1][2][3][4][5][6][7][8][9] However, we still face some challenges for the practical application, such as the reflection geometry makes it inconvenient for practical applications due to the interference between incident and reflected waves. 10 Besides, the metallic film with a thickness smaller than skin depth is high transparent for visible light and half transparent for infrared light, [11][12][13][14] but some transmission devices with larger thickness are typically not perfectly transparent for electromagnetic waves, [15][16][17][18] so the energy loss issues remains unsolved.…”

Complementary Y-shaped chiral metamaterial with giant optical activity and circular dichroism simultaneously for terahertz waves

“…At 2.14 THz, the directions of H 2 and H 3 are deviated to the incident electric field E in , thus never contributing to the polarization rotation. The induced magnetic field H 1 is along y-axis and originate from the interlayer near-field coupling between two twisted layers (16,31,43). All the field patterns will be twisted inside the CYCMM structure as a consequence of interlayer coupling around these resonant frequencies.…”

“…In particular, the manipulation of THz waves in modern optical devices is important in some areas of imaging, scanning and communication sciences (28)(29)(30)(31)(32). The development of CMMs with giant optical activity and/or large CD effect is especially important due to lack of natural materials for manipulating the THz waves (6).…”

Broadband circular polarizers constructed using helix-like chiral metamaterials

“…[14][15][16] In addition, they are usually realized with multiple conventional lithography or electron beam lithographic techniques, which are important fabrication processes for sub-wavelength gratings. [17][18][19] 25 their selective effects to circular polarizations are mainly resulted from the coupling of upper and lower layers, which are still narrow band effect. In 2012, Zhao et.al reported a kind of twisted metamaterials based on closely spaced twisted broadband bianisotropic gold nanorod arrays.…”