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Metamaterials open up various exotic means to control electromagnetic waves and among them polarization manipulations with metamaterials have attracted intense attention. As of today, static responses of resonators in metamaterials lead... more
Metamaterials open up various exotic means to control electromagnetic waves and among them
polarization manipulations with metamaterials have attracted intense attention. As of today, static
responses of resonators in metamaterials lead to a narrow-band and single-function operation.
Extension of the working frequency relies on multilayer metamaterials or different unit cells, which
hinder the development of ultra-compact optical systems. In this work, we demonstrate a switchable
ultrathin terahertz quarter-wave plate by hybridizing a phase change material, vanadium dioxide
(VO2), with a metasurface. Before the phase transition, VO2 behaves as a semiconductor and the
metasurface operates as a quarter-wave plate at 0.468THz. After the transition to metal phase,
the quarter-wave plate operates at 0.502THz. At the corresponding operating frequencies, the
metasurface converts a linearly polarized light into a circularly polarized light. This work reveals the
feasibility to realize tunable/active and extremely low-profile polarization manipulation devices in
the terahertz regime through the incorporation of such phase-change metasurfaces, enabling novel
applications of ultrathin terahertz meta-devices.
polarization manipulations with metamaterials have attracted intense attention. As of today, static
responses of resonators in metamaterials lead to a narrow-band and single-function operation.
Extension of the working frequency relies on multilayer metamaterials or different unit cells, which
hinder the development of ultra-compact optical systems. In this work, we demonstrate a switchable
ultrathin terahertz quarter-wave plate by hybridizing a phase change material, vanadium dioxide
(VO2), with a metasurface. Before the phase transition, VO2 behaves as a semiconductor and the
metasurface operates as a quarter-wave plate at 0.468THz. After the transition to metal phase,
the quarter-wave plate operates at 0.502THz. At the corresponding operating frequencies, the
metasurface converts a linearly polarized light into a circularly polarized light. This work reveals the
feasibility to realize tunable/active and extremely low-profile polarization manipulation devices in
the terahertz regime through the incorporation of such phase-change metasurfaces, enabling novel
applications of ultrathin terahertz meta-devices.
Research Interests:
This work presents analytical, numerical and experimental demonstrations of light diffracted through a logarithmic spiral (LS) nanoslit, which forms a type of switchable and focustunable structure. Owing to a strong dependence on the... more
This work presents analytical, numerical and experimental demonstrations of light diffracted through a logarithmic
spiral (LS) nanoslit, which forms a type of switchable and focustunable structure. Owing to a strong dependence on the incident photon spin, the proposed LS-nanoslit converges incoming
light of opposite handedness (to that of the LS-nanoslit) into a
confined subwavelength spot, while it shapes light with similar
chirality into a donut-like intensity profile. Benefitting from the
varying width of the LS-nanoslit, different incident wavelengths
interfere constructively at different positions, i.e., the focal length
shifts from 7.5 μm (at λ = 632.8 nm) to 10 μm (at λ = 488 nm),
which opens up new opportunities for tuning and spatially separating broadband light at the micrometer scale.
spiral (LS) nanoslit, which forms a type of switchable and focustunable structure. Owing to a strong dependence on the incident photon spin, the proposed LS-nanoslit converges incoming
light of opposite handedness (to that of the LS-nanoslit) into a
confined subwavelength spot, while it shapes light with similar
chirality into a donut-like intensity profile. Benefitting from the
varying width of the LS-nanoslit, different incident wavelengths
interfere constructively at different positions, i.e., the focal length
shifts from 7.5 μm (at λ = 632.8 nm) to 10 μm (at λ = 488 nm),
which opens up new opportunities for tuning and spatially separating broadband light at the micrometer scale.
Research Interests:
The focusing performance of a 40 nm-thick metasurface lens is experimentally demonstrated. The longitudinal multifoci flat metasurface lens is illuminated with a linearly polarized light (|LP>) beam at normal incidence. Three focal planes... more
The focusing performance of a 40 nm-thick metasurface lens is experimentally demonstrated. The longitudinal multifoci flat metasurface lens is illuminated with a linearly polarized light (|LP>) beam at normal incidence. Three focal planes with circular polarization states (|L> and |R>) are observed. The theoretical intensity profile of the light behind the metalens in the y–z plane agrees well with theoretical predictions.
Research Interests:
Orbital angular momentum (OAM) has been an enthralling topic of research from fundamental physics to technological applications since its discovery in 1992. Many techniques have been developed to generate OAM such as using spiral phase... more
Orbital angular momentum (OAM) has been an enthralling topic of research from fundamental
physics to technological applications since its discovery in 1992. Many techniques have been developed to generate OAM such as using spiral phase plates (SPPs), computer-generated holograms
(CGH) and cylindrical mode converters, etc. However, these methods are based on bulky optics
that cause a major hindrance for their exploitation in the emerging area of micron-nanophotonics.
Recently, generation of such helical beams by micron-sized structures has gained momentous
interest to make their appliance possible at small scale. This paper recapitulates these endeavors of
minuscule optical vortex generation. Five di®erent types of compact optical vortex generators, i.e.,
downscaling of conventional OAM generators, plasmonic vortex lens (PVLs), metasurfaces, integrated OAM emitters and subwavelength apertures are brought under discussion.
physics to technological applications since its discovery in 1992. Many techniques have been developed to generate OAM such as using spiral phase plates (SPPs), computer-generated holograms
(CGH) and cylindrical mode converters, etc. However, these methods are based on bulky optics
that cause a major hindrance for their exploitation in the emerging area of micron-nanophotonics.
Recently, generation of such helical beams by micron-sized structures has gained momentous
interest to make their appliance possible at small scale. This paper recapitulates these endeavors of
minuscule optical vortex generation. Five di®erent types of compact optical vortex generators, i.e.,
downscaling of conventional OAM generators, plasmonic vortex lens (PVLs), metasurfaces, integrated OAM emitters and subwavelength apertures are brought under discussion.
Research Interests:
Dynamic generation of obitial angular momentum (OAM) of light has enabled complex manipulation of micro-particles, high-dimension quantum entanglement and optical communication. We report an analog vortex transmitter made of one... more
Dynamic generation of obitial angular momentum (OAM) of light has enabled
complex manipulation of micro-particles, high-dimension quantum entanglement and
optical communication. We report an analog vortex transmitter made of one bilaterally
symmetric grating and an aperture, emitting optical vortices with the average OAM
value continuously variant in the entire rational range. Benefiting from linearly-varying
transverse dislocation along its axis of symmetry, this diffractive transmitter possesses
extra degree of freedom in engineering broadband optical vortices meanwhile
preserving a novel spiniform phase with equally spaced singularities. It unlimitedly
increases the average OAM of light by embracing more singularities, which is
significantly different from that for Laguerre-Gaussian (LG) and Bessel vortex beams.
Realizing analog generation of OAM in a single device, this technique can be potentially
extended to other frequencies and applied to a wide spectrum of developments on
quantum physics, aperiodic photonics and optical manipulation.
complex manipulation of micro-particles, high-dimension quantum entanglement and
optical communication. We report an analog vortex transmitter made of one bilaterally
symmetric grating and an aperture, emitting optical vortices with the average OAM
value continuously variant in the entire rational range. Benefiting from linearly-varying
transverse dislocation along its axis of symmetry, this diffractive transmitter possesses
extra degree of freedom in engineering broadband optical vortices meanwhile
preserving a novel spiniform phase with equally spaced singularities. It unlimitedly
increases the average OAM of light by embracing more singularities, which is
significantly different from that for Laguerre-Gaussian (LG) and Bessel vortex beams.
Realizing analog generation of OAM in a single device, this technique can be potentially
extended to other frequencies and applied to a wide spectrum of developments on
quantum physics, aperiodic photonics and optical manipulation.
Research Interests:
Recent developments have shown that light’s orbital angular momentum (OAM) can be harnessed for a diversity of emerging applications and generated by miniaturized OAM generators. Nanostructured flat logarithmic-spiral zone plates (LSZPs)... more
Recent developments have shown that light’s orbital angular momentum (OAM) can be harnessed for a diversity of emerging applications and generated by miniaturized OAM generators. Nanostructured flat logarithmic-spiral zone
plates (LSZPs) are proposed to produce as well as focus optical vortices with a long focal depth in the broadband visible range. Topologically breaking the in-plane symmetry, this nanoengineered LSZP continuously modulates both
amplitude and phase in the diffraction field to shape twisted focusing of the optical vortex beam, which is microscopically confined and spatially spiraling with variant crescent-shaped transverse intensity profiles. Owing to its rich structural degree of freedom upon aperiodic and continuously variant features, the LSZP provides a compact solution to generate and control optical vortices carrying scalable OAM and highly concentrated photons with a high transmission efficiency of ∼22%. This can offer new opportunities for 3D light shaping,
plates (LSZPs) are proposed to produce as well as focus optical vortices with a long focal depth in the broadband visible range. Topologically breaking the in-plane symmetry, this nanoengineered LSZP continuously modulates both
amplitude and phase in the diffraction field to shape twisted focusing of the optical vortex beam, which is microscopically confined and spatially spiraling with variant crescent-shaped transverse intensity profiles. Owing to its rich structural degree of freedom upon aperiodic and continuously variant features, the LSZP provides a compact solution to generate and control optical vortices carrying scalable OAM and highly concentrated photons with a high transmission efficiency of ∼22%. This can offer new opportunities for 3D light shaping,
Research Interests:
This letter presents a new method of cross-range scaling in inverse synthetic aperture radar (ISAR) imaging. The effective rotational velocity (ERV), being the crucial factor for scaling, is generally unknown for noncooperative... more
This letter presents a new method of cross-range
scaling in inverse synthetic aperture radar (ISAR) imaging. The
effective rotational velocity (ERV), being the crucial factor for
scaling, is generally unknown for noncooperative objects. By
considering the degradation from target rotation, the proposed
scheme estimates ERV based on image sharpness maximization.
A range deviator induced by the center shift is also embedded in
the estimation process. The cross-range scaling factor with an enhanced ISAR image can be obtained by an efficient Gauss–Newton
method. The results acquired from both the simulations and real
data experiments validate the effectiveness and robustness of the
proposed method.
scaling in inverse synthetic aperture radar (ISAR) imaging. The
effective rotational velocity (ERV), being the crucial factor for
scaling, is generally unknown for noncooperative objects. By
considering the degradation from target rotation, the proposed
scheme estimates ERV based on image sharpness maximization.
A range deviator induced by the center shift is also embedded in
the estimation process. The cross-range scaling factor with an enhanced ISAR image can be obtained by an efficient Gauss–Newton
method. The results acquired from both the simulations and real
data experiments validate the effectiveness and robustness of the
proposed method.
Research Interests:
Research Interests:
Research Interests:
Research Interests:
In this paper, the high frequency electromagnetic field expressions for two dimensional Cassegrain system embedded in a chiral medium are presented. Due to failure of Geometrical Optics (GO) at the caustic region, Maslov’s method is used... more
In this paper, the high frequency electromagnetic field
expressions for two dimensional Cassegrain system embedded in a
chiral medium are presented. Due to failure of Geometrical Optics
(GO) at the caustic region, Maslov’s method is used to find the field
expressions. Two different cases have been analyzed. Firstly, the
chirality parameter (kβ) is adjusted to support positive phase velocity
(PPV) for both left circularly polarized (LCP) and right circularly
polarized (RCP) modes traveling in the medium. Secondly, kβ is
adjusted such that one mode travels with PPV, and the other mode
travels with negative phase velocity (NPV). The results for both cases
are presented in the paper.
expressions for two dimensional Cassegrain system embedded in a
chiral medium are presented. Due to failure of Geometrical Optics
(GO) at the caustic region, Maslov’s method is used to find the field
expressions. Two different cases have been analyzed. Firstly, the
chirality parameter (kβ) is adjusted to support positive phase velocity
(PPV) for both left circularly polarized (LCP) and right circularly
polarized (RCP) modes traveling in the medium. Secondly, kβ is
adjusted such that one mode travels with PPV, and the other mode
travels with negative phase velocity (NPV). The results for both cases
are presented in the paper.
Research Interests:
Research Interests:
In this paper, the high frequency electromagnetic field expressions for two dimensional Cassegrain system embedded in a chiral medium are presented. Due to failure of Geometrical Optics (GO) at the caustic region, Maslov’s method is used... more
In this paper, the high frequency electromagnetic field
expressions for two dimensional Cassegrain system embedded in a
chiral medium are presented. Due to failure of Geometrical Optics
(GO) at the caustic region, Maslov’s method is used to find the field
expressions. Two different cases have been analyzed. Firstly, the
chirality parameter (kβ) is adjusted to support positive phase velocity
(PPV) for both left circularly polarized (LCP) and right circularly
polarized (RCP) modes traveling in the medium. Secondly, kβ is
adjusted such that one mode travels with PPV, and the other mode
travels with negative phase velocity (NPV). The results for both cases
are presented in the paper.
expressions for two dimensional Cassegrain system embedded in a
chiral medium are presented. Due to failure of Geometrical Optics
(GO) at the caustic region, Maslov’s method is used to find the field
expressions. Two different cases have been analyzed. Firstly, the
chirality parameter (kβ) is adjusted to support positive phase velocity
(PPV) for both left circularly polarized (LCP) and right circularly
polarized (RCP) modes traveling in the medium. Secondly, kβ is
adjusted such that one mode travels with PPV, and the other mode
travels with negative phase velocity (NPV). The results for both cases
are presented in the paper.
Research Interests:
Featuring shorter wavelengths and high photon energy, ultraviolet (UV) light enables many exciting applications including photolithography, sensing, high-resolution imaging, and optical communication. The conventional methods of UV light... more
Featuring shorter wavelengths and high photon energy, ultraviolet (UV) light enables many exciting applications including photolithography, sensing, high-resolution imaging, and optical communication. The conventional methods of UV light manipulation through bulky optical components limit their integration in fast-growing on-chip systems. The advent of metasurfaces promised unprecedented control of electromagnetic waves from microwaves to visible spectrums. However, the availability of suitable and lossless dielectric material for the UV domain hindered the realization of highly efficient UV metasurfaces. Here, a bandgap-engineered silicon nitride (Si3N4) material is used as a best-suited candidate for all-dielectric highly efficient UV metasurfaces. To demonstrate the wavefront manipulation capability of the Si3N4 for the UV spectrum, we design and numerically simulate multiple all-dielectric metasurfaces for the perfect vortex beam generation by combing multiple phase profiles int...