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Radial cross-section of the electric field components Er, Ez and time-averaged Poynting vector <Sz> of the TM0,1 mode of a cylindrical metallic waveguide (a) with a radius a = 0.45λ, and (b) with a radius a = 5λ.
Source publication
We report on unidirectional and asymmetric transmission of radially polarized THz radiation through a dual circular metallic grating with sub-wavelength slits. Unidirectional transmission is shown theoretically for a super-Gaussian incident beam, and an asymmetric transmission is demonstrated experimentally, when the radially polarized beam of 0.1...
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Citations
... 8 Recently, metamaterials have been studied widely by simulation methods; most of the sample fabrications and experimental measurements were just realized at microwave and terahertz regions by both two-dimensional (2D) and three-dimensional (3D) metamaterials. 1,2,9 In contrast, the fabrication of nanoscale metastructures at infrared and optical regions primarily involve planar metasurfaces rather than 3D metamaterials. 7,10,11 However, it is of great signicance to overcome the challenges of fabricating 3D metamaterials at nanoscale, which have presented or enhanced a variety of electromagnetic properties not realized in planar metamaterials, such as AT effect of linearly polarized light 12,13 and the enhanced optical activity. ...
... However, these studies usually involve a material whose size is bigger than the desired wavelength; hence, they cannot be used in the micro-nano optical system and other optical communication systems. In addition, the gradient metasurface, 25 asymmetric gratings, 9,26,27 and chiral metamaterials 28,29 have been proposed to realize AT effects without breaking Lorentz's reciprocity theorem. It is complicated to properly design the phase gradient of the metasurface 25 or to avoid the higher diffraction modes of asymmetric gratings. ...
A bi-layer continuous omega-shaped metamaterial was proposed and fabricated to measure the asymmetric transmission (AT) effect of a linearly polarized light at near-infrared region. The metamaterial was fabricated by the electron-beam lithography method, and the AT effect was demonstrated by the difference between total transmittances in the two opposite propagation directions for x-/y-polarized incident light. The experimental results were confirmed by the full-wave simulated results. Importantly, we also experimentally demonstrated that the AT effect is robust against the misalignments between the first and the second omega-shaped layers. Accordingly, the successfully prepared sample and its characterization provide a bright future for applications in light-controlled switchers and optical diodes in on-chip optical systems and information communication systems.
... Asymmetric transmission has been observed in diffraction-based elements with different number of diffraction orders at two sides [2,11,12]. We have recently developed double gratings for sub-THz waves -an optimized planar grating for broadband operation [17] for the transverse magnetic polarization, and a circular double grating for a radially polarized wave [18]. These gratings are the subject of the present communication. ...
... Transmission of light through a circular hole or slit has been a long-lasting subject of research [19][20][21][22][23][24][25][26][27][28][29]. In Ref. [18], the double concentric sub-wavelength gratings have been designed in such a way, that the transmission is unidirectional, and is combined with focusing. ...
... The other double grating of interest consists of two gratings, each of which contains several circular subwavelength slits [18]. The radial period is larger than the wavelength on one of the sides, and smaller on the other. ...
We have developed a metallic double circular grating with sub-wavelength slits which blocks radially polarized light incident from one of its sides and acts as a focusing diffractive element in the other direction. The proposed grating has been optimized for the sub-THz frequency range. Unidirectional transmission through the grating has been demonstrated experimentally at 0.1 THz. We have also developed a planar metallic double grating with sub-wavelength slits which blocks light with a transverse magnetic polarization incident from one of the grating sides and transmits radiation incident from the opposite direction into the +1 and -1 diffraction orders. These gratings which could be used as unidirectional couplers consist of optically linear materials and their operation respects the Lorentz reciprocity theorem.
Recent demonstrations of deep- and vacuum-ultraviolet (DUV and VUV) light emission from artificially engineered meta-atoms through nonlinear harmonic signal generation processes have opened up new avenues for fundamental engineering approaches and modern applications. While many different phenomena based on optical metasurfaces have been revealed in linear optics, several studies have reported the observation of various nonlinear optical phenomena in such nanosystems, like, for example, second and third harmonic generation (SHG and THG), multiphoton luminescence, higher harmonic generation, and four-wave mixing. Plasmonic and all-dielectric flatland metasurfaces enable successful manipulation of light–matter interactions on ultradense platforms and provide substantial enhancement of driving fields, which make these architectures promising and attractive to efficiently radiate intense and coherent second and third harmonic radiations. In this focused Review, we highlight and discuss the recent state-of-the-art methods that have been developed and proposed for the generation of nonlinear harmonic signal and high-energy DUV and VUV lights. This contribution not only summarizes the strategies that have been exploited for augmenting the intensity of nonlinear UV signal, but also introduces the novel mechanisms to strongly optimize the conversion efficiency of this principle. We envisage that this understanding allows to compare the performance of versatile nonlinear DUV and VUV metasources and paves the way of designing much more efficient light emitting tools such as lasers, super-resolution imaging nanosystems, and nanolithography apertures.
