Transparent conducting oxides are part of a robust material class that is capable of supporting near-IR surface plasmon resonances (SPRs) which are strongly dependent on size, structure, and doping of the material. This study presents the implementation of holographic lithography to structure large area square lattice cylindrical hole arrays on the transparent conducting oxide thin film, aluminum doped zinc oxide (AZO). For fabricated structures on a glass substrate, SPR are indirectly measured by FTIR transmission and verified with electromagnetic simulations using a finite difference time domain method. Furthermore, it is shown that the SPR excited are standing wave resonances in the (1,1) direction of the lattice array located at the interface of the patterned AZO and glass substrate. This research extends the robust CMOS compatible fabrication techniques of holographic lithography into tunable conductive materials,and contributes to the core technology of future integrated photonics.
In this paper, we proposed highly efficient all-dielectric Huygens’ metasurfaces working at mid-IR frequencies. The meta-atom of the designed Huygens’ metasurface is a cubic dielectric resonator or its variety, which is made from PbTe that possesses a high refractive index of around 5 at mid-IR frequencies. By overlapping spectrally both the magnetic and electric dipole modes of the high-index dielectric resonators, a full phase coverage of 2π and an equal-magnitude transmission could be achieved, which are essential conditions for realizing a metasurface. Two Huygens’ metasurfaces for beam bending are designed with a phase change between two consecutive meta-atoms of π/4 and π/3, respectively. The simulation results agree well with the design theory.
In this paper, we proposed metasurfaces working at two THz wavelengths simultaneously (in a broadband manner for each wavelength). The performance of the proposed metasurfaces at both wavelengths could be manipulated individually. A unit cell of the metasurface is first designed. Based on the unit cell structure, two functional metasurface devices are realized, which can arbitrarily deflect the incident THz waves at the two design wavelengths. The simulation results of these two proposed designs agree well with the theoretical predictions.
In this paper, we proposed a novel cross-polarization converter that simultaneously works at two frequencies in the reflection mode, which is constructed of an L-shape perforated graphene sheet printed on a dielectric spacer backed by a gold layer. For the normal incidence, the optical rotation at these two working frequencies originates from the simultaneous excitation of both eigenmodes characterized as the localized surface plasmon resonances. In addition, both working frequencies can be tuned within a large frequency range by varying the Fermi energy of the graphene, which opens up tremendous opportunities to develop voltage-controlled tunable devices at mid-IR frequencies.
In this paper, we proposed novel graphene-based tunable plasmonic metamaterial structures to realize transparency windows. The proposed structures are composed of a graphene layer perforated with a quadrupole slot structure and a dolmen-like slot structure, which could achieve single and multiple transparency windows, respectively. In both complementary structures, the transparency windows could be dynamically manipulated by varying the Fermi energy levels of the graphene layer through electrical gating. The presented complementary graphene-based metamaterial structures with multiple tunable transparency windows could open up new opportunities for potential applications in tunable multi-wavelength slow light devices and optical sensors.
In this paper, a novel design of broadband monopole optical nano-antennas is proposed. It consists of a corrugated halfelliptical patch inside an elliptical aperture. Full-wave electromagnetic simulations have been used to investigate the performance of the nano-antenna. The predicted performance of the proposed monopole nano-antenna is remarkably broadband. Moreover, the proposed broadband nano-antenna can respond to light waves with different polarizations. The proposed optical antenna will pave the way towards the development of high performance optical antennas and optical systems.