4 Chirality and Antiferromagnetism in Optical Metasurfaces
79
computing capacities are popularized to assist the design and manufacture of optical
nano-structures. The first optical metasurfaces were reported in 1998 by Simion
Astilean, Philippe Lalanne and their collaborators to demonstrate the blazed gratings with spatially varied subwavelength features of TiO 2 on a quartz substrate at
the working wavelength of 633 nm [7, 8]. The phase modulation is controlled by
the filling factor of size-varied subwavelength structures in a pixel pitch, with the
guidance of effective medium theory. The measured efficiency of 1-order diffraction is 83%, which is slightly larger than the theoretical prediction and indicates a
fundamental breakthrough as a novel element. Although further demonstration of
meta-lenses is also done with good agreement, the potential of these subwavelength
structures has not been fully recognized due to the rough design tools of effective
medium theory that ignores the local response of confined nanomodes and the unpolarized illumination that excludes the deep investigation into polarization effects. In
addition, the product yield of these devices is lower due to the challenging fabrication
at that moment. As a result, these excellent works at their group terminate so that
they are not widely exposed among the optics community until recently.
Since 2000, Hasman group reported a series of works that utilized the rotating
subwavelength metal or dielectric nanorods to control the phase and polarization of
light by introducing the important concept of geometric phase or Berry phase [9,
10, 24–26]. Compared with the size-varied subwavelength structures developed by
Philippe Lalanne et al., geometric metasurfaces with size-fixed nanorodes offer much
higher level of phase modulation because the geometric phase is determined by the
rotating angle of nanorodes without changing their dimension, hereby facilitating
the fabrication due to uniformly distributed nanostructures. With this powerful platform of geometric metasurfaces, Hasman group demonstrated many novel devices
such as cylindrical vector beams, polarization-dependent hologram and lenses at
the infrared wavelengths. These works highlight the significance of subwavelength
devices and therefore play an important role in developing and popularizing various
optical meta-devices with polarization features. Considering that the dominated electromagnetic resonances existing in geometric metasurfaces were not unveiled clearly
at that moment, these metal or dielectric geometric metasurfaces, operating in a
transmission mode that is preferred in most optical equipment and systems, were
not designed with the suitable geometry and materials, leading to low efficiency for
practical applications.
With the rapid development of metamaterials for applications such as perfect lens
and electromagnetic cloaking, the interest of utilizing subwavelength structures to
control the waves increases quickly among the entire electromagnetic community.
The related computing algorithms such as finite-element method (FEM) and timedomain finite-difference (FDTD) method are available at low cost and carried out
even at a personal computer, which extremely decreases the threshold of simulating
the electromagnetic responses of optical nano-structures. In 2011, Federico Capasso
et al. developed size-varied V-shape structures with deep-subwavelength features to
tailor the discrete phase of a linearly polarized light (perpendicular to the incident
polarization) for blazed gratings and vortex generation at the mid-infrared wavelengths [11]. It offers the first time demonstration of manipulating the phase and
79
computing capacities are popularized to assist the design and manufacture of optical
nano-structures. The first optical metasurfaces were reported in 1998 by Simion
Astilean, Philippe Lalanne and their collaborators to demonstrate the blazed gratings with spatially varied subwavelength features of TiO 2 on a quartz substrate at
the working wavelength of 633 nm [7, 8]. The phase modulation is controlled by
the filling factor of size-varied subwavelength structures in a pixel pitch, with the
guidance of effective medium theory. The measured efficiency of 1-order diffraction is 83%, which is slightly larger than the theoretical prediction and indicates a
fundamental breakthrough as a novel element. Although further demonstration of
meta-lenses is also done with good agreement, the potential of these subwavelength
structures has not been fully recognized due to the rough design tools of effective
medium theory that ignores the local response of confined nanomodes and the unpolarized illumination that excludes the deep investigation into polarization effects. In
addition, the product yield of these devices is lower due to the challenging fabrication
at that moment. As a result, these excellent works at their group terminate so that
they are not widely exposed among the optics community until recently.
Since 2000, Hasman group reported a series of works that utilized the rotating
subwavelength metal or dielectric nanorods to control the phase and polarization of
light by introducing the important concept of geometric phase or Berry phase [9,
10, 24–26]. Compared with the size-varied subwavelength structures developed by
Philippe Lalanne et al., geometric metasurfaces with size-fixed nanorodes offer much
higher level of phase modulation because the geometric phase is determined by the
rotating angle of nanorodes without changing their dimension, hereby facilitating
the fabrication due to uniformly distributed nanostructures. With this powerful platform of geometric metasurfaces, Hasman group demonstrated many novel devices
such as cylindrical vector beams, polarization-dependent hologram and lenses at
the infrared wavelengths. These works highlight the significance of subwavelength
devices and therefore play an important role in developing and popularizing various
optical meta-devices with polarization features. Considering that the dominated electromagnetic resonances existing in geometric metasurfaces were not unveiled clearly
at that moment, these metal or dielectric geometric metasurfaces, operating in a
transmission mode that is preferred in most optical equipment and systems, were
not designed with the suitable geometry and materials, leading to low efficiency for
practical applications.
With the rapid development of metamaterials for applications such as perfect lens
and electromagnetic cloaking, the interest of utilizing subwavelength structures to
control the waves increases quickly among the entire electromagnetic community.
The related computing algorithms such as finite-element method (FEM) and timedomain finite-difference (FDTD) method are available at low cost and carried out
even at a personal computer, which extremely decreases the threshold of simulating
the electromagnetic responses of optical nano-structures. In 2011, Federico Capasso
et al. developed size-varied V-shape structures with deep-subwavelength features to
tailor the discrete phase of a linearly polarized light (perpendicular to the incident
polarization) for blazed gratings and vortex generation at the mid-infrared wavelengths [11]. It offers the first time demonstration of manipulating the phase and