Abstract:Huygens' meta-atom is the basic building unit of Huygens' metasurfaces allowing for almost arbitrary wavefront shaping across a surface. We here present a kind of Huygens' meta-atom by coupling a nanodisk to its Babinet-complementary structure (nanohole), and develop an optical lumped nanocircuit model to analyze vertical and lateral coupling effects and resonance frequencies. Simulation results show that the tuned coupling via lateral misalignment between the two nanostructures is sufficient to shape the wave… Show more
“…That is, the sum width of the two Ag strips is exactly equal to the period 900 nm, i.e., d = a + l , therefore the two gratings are geometrically complementary to each other. As the SiO 2 dielectric spacer layer is very thin with a thickness t s = 200 nm, strong near-field coupling effect exists between the upper and lower gratings 27,30,32 .Figure 1Device structure. ( a ) Schematic diagram and ( b ) cross-section view of the AT device.…”
Section: Device Structure and Operation Principlementioning
confidence: 99%
“…The second distinct feature of our AT device is that, the bilayer gratings are of coupled complementary structure. It is well known that near-field coupling effect inherently exists in such structures 27,30 . As demonstrated later, this near-field coupling effect, through the coherence interference of electric- and magnetic-dipole moments and Kerker conditions, can greatly enhance forward transmittance at operation wavelength, increase AT effect, and also determine operation bandwidth.…”
Section: Device Structure and Operation Principlementioning
confidence: 99%
“…When an x -polarized wave normally illuminates the AT device along the positive z -axis (i.e, the forward propagation direction), the light first hits the upper grating and excites electric-dipole moment p x along the x -axis, and according to the Babinet’s law 27,36–38 , the lower grating will be induced an antiparallel current to form a magnetic-dipole moment m y along the y -direction. Then the normalized forward/backward (i.e., along the positive or negative z -axis) scattering cross section can be expressed as 34,35,39 :where k is the wavenumber in a background material with electric permittivity ɛ = ɛ 0 ɛ r , c is the speed of light in free space, and | E inc | is the amplitude of the incident electric field.…”
Section: Device Structure and Operation Principlementioning
confidence: 99%
“…In this paper, we propose an AT device based on coupled complementary subwavelength gratings. According to Babinet’s law, coupled complementary bilayer structures naturally possess electric and effective magnetic responses over a wide range of electromagnetic spectrum 26,27 . The strong coupling effects inherently existing in the bilayer structures can provide strong light-matter interactions and multi-dimensional control on electromagnetic waves, therefore having significant advantages in improving the performances of nanophotonic devices 28 .…”
Asymmetric transmission (AT) devices are fundamental elements for optical computing and information processing. We here propose an AT device consisting of a pair of coupled complementary subwavelength gratings. Different from previous works, asymmetric dielectric environment is employed for unidirectional excitation of surface plasmon polaritons (SPPs) and thus asymmetric optical transmission, and near-field coupling effect inherent in the coupled complementary structure is exploited to enhance forward transmission and AT behavior, and determine operation bandwidth as well. The influence of asymmetric dielectric environment, effect of vertical and lateral couplings, interactions of electric- and magnetic-dipole moments and the realization of Kerker conditions, are investigated in depth to unearth the AT mechanism and performance. High-performance AT with large forward transmittance of 0.96 and broad bandwidth of 174 nm is achieved at wavelength 1250 nm. Our work helps people to gain a better understanding of near-filed coupling effect in coupled complementary structures, expand their application fields, and it also offers an alternate way to high-performance AT devices.
“…That is, the sum width of the two Ag strips is exactly equal to the period 900 nm, i.e., d = a + l , therefore the two gratings are geometrically complementary to each other. As the SiO 2 dielectric spacer layer is very thin with a thickness t s = 200 nm, strong near-field coupling effect exists between the upper and lower gratings 27,30,32 .Figure 1Device structure. ( a ) Schematic diagram and ( b ) cross-section view of the AT device.…”
Section: Device Structure and Operation Principlementioning
confidence: 99%
“…The second distinct feature of our AT device is that, the bilayer gratings are of coupled complementary structure. It is well known that near-field coupling effect inherently exists in such structures 27,30 . As demonstrated later, this near-field coupling effect, through the coherence interference of electric- and magnetic-dipole moments and Kerker conditions, can greatly enhance forward transmittance at operation wavelength, increase AT effect, and also determine operation bandwidth.…”
Section: Device Structure and Operation Principlementioning
confidence: 99%
“…When an x -polarized wave normally illuminates the AT device along the positive z -axis (i.e, the forward propagation direction), the light first hits the upper grating and excites electric-dipole moment p x along the x -axis, and according to the Babinet’s law 27,36–38 , the lower grating will be induced an antiparallel current to form a magnetic-dipole moment m y along the y -direction. Then the normalized forward/backward (i.e., along the positive or negative z -axis) scattering cross section can be expressed as 34,35,39 :where k is the wavenumber in a background material with electric permittivity ɛ = ɛ 0 ɛ r , c is the speed of light in free space, and | E inc | is the amplitude of the incident electric field.…”
Section: Device Structure and Operation Principlementioning
confidence: 99%
“…In this paper, we propose an AT device based on coupled complementary subwavelength gratings. According to Babinet’s law, coupled complementary bilayer structures naturally possess electric and effective magnetic responses over a wide range of electromagnetic spectrum 26,27 . The strong coupling effects inherently existing in the bilayer structures can provide strong light-matter interactions and multi-dimensional control on electromagnetic waves, therefore having significant advantages in improving the performances of nanophotonic devices 28 .…”
Asymmetric transmission (AT) devices are fundamental elements for optical computing and information processing. We here propose an AT device consisting of a pair of coupled complementary subwavelength gratings. Different from previous works, asymmetric dielectric environment is employed for unidirectional excitation of surface plasmon polaritons (SPPs) and thus asymmetric optical transmission, and near-field coupling effect inherent in the coupled complementary structure is exploited to enhance forward transmission and AT behavior, and determine operation bandwidth as well. The influence of asymmetric dielectric environment, effect of vertical and lateral couplings, interactions of electric- and magnetic-dipole moments and the realization of Kerker conditions, are investigated in depth to unearth the AT mechanism and performance. High-performance AT with large forward transmittance of 0.96 and broad bandwidth of 174 nm is achieved at wavelength 1250 nm. Our work helps people to gain a better understanding of near-filed coupling effect in coupled complementary structures, expand their application fields, and it also offers an alternate way to high-performance AT devices.
Combining two or several functionalities into a single metadevice is of significant importance and attracts growing interest in recent years. We here introduce the concept of modularization design in dual-wavelength multifunctional metadevice, which is composed of a lower metasurface and an upper metasurface with an indium-tin-oxide (ITO) layer. Benefiting from the fact that ITO holds high infrared (IR) reflection while transparence at visible wavelengths, the metadevice can work in reflection and transmission modes at two very distinct wavelengths, one is 2365 nm in the IR band and the other 650 nm in the visible range. More interestingly and importantly, the two metasurface layers with different functionalities are easy to flexibly integrate into a series of dual-wavelength multifunctional metadevices, with negligible interaction between them and no need of re-designing or re-optimizing their structure parameters. Based on modularization design and functional integration, four kinds of dual-wavelength multifunctional metadevices are demonstrated, which can perform reflective deflection/focusing at 2365 nm and transmissive deflection/focusing at 650 nm. We believe our work may open a straight-forward and flexible way in designing multi-wavelength multifunctional metadevices and photonic integrated devices.
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