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.
Gradient index (GRIN) structures have attracted great interests since their invention. Especially, the recent advance in
the fields of transformation optics, plasmonics, and nanofabrication techniques has opened new directions for the
applications of GRIN structures in nano-photonic devices. In this paper, we apply Luneburg lens and its transformed
counterpart to realize efficient coupling to plasmonic nano-waveguides. We first briefly present the general structures of
Luneburg lens and generalized Luneburg lens, as well as the design process of flattened Luneburg lens applying quasiconformal
mapping techniques. After that, we study the performance of these lenses for coupling electromagnetic signals
to nano-waveguides (the metal-insulator-metal (MIM) nano-waveguide), and different schemes are investigated.
Here we present single exposure holographic fabrication of embedded defects in photonic crystal structures in a negative photoresist using a spatial light modulator (SLM). A phase pattern is engineered to form a desired interference pattern and displayed on a phase-only SLM. The resulting first order beams at the Fourier plane are used to recreate the interference pattern. Negative and positive defects are added to the photonic crystal in the following ways. A void-type defect is produced in two dimensional photonic crystal structures by replacing the phase of the engineered phase pattern with a constant value at the points where the defect is desired. And a positive bump defect can be made by allowing the zeroth order beam to interfere with the first order beams. Through these methods, it is possible to fabricate arbitrary shaped defect structures in photonic crystals through a single exposure process, thus improving cost effectiveness and simplifying the fabrication process of integrated photonics.
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.
In this work, we present a method of holographically fabricating photonic structures in photosensitive polymer
using a phase pattern displayed on a spatial light modulator (SLM) as a digitally programmable phase mask. The phase
pattern can be programmed in hexagonal and square symmetries. By changing the gray level of the pixelated units in the
displayed phase pattern, we can achieve a digital control of the phases of one or more of the interfering beams, thus
changing the interference pattern. By using the phase pattern on the SLM as a tunable phase mask, different photonic
crystal templates can be fabricated.
It is well-known that the conventional lens design suffers from the aberration, which will lead to imperfect imaging. One
way to solve this problem is to use gradient index (GRIN) lenses such as Luneburg lens. However, the spherical
geometry of Luneburg lens imposes difficulty for manufacturing. Also, it is desired to design the Luneburg lens with
arbitrary focal length. To address these issues, in this paper, we propose to apply the transformation optics techniques to
the general Luneburg lens design. In this way, the spherical lens surface will be transformed to flattened shapes, which
can be practically fabricated on a flat substrate. Specifically, three-dimensional (3D) Luneburg lenses with different
focal lengths will be studied. Moreover, discussion on the fabrications of proposed lens has been included. It is desired
to ensure that the modified design lies within the available material properties of various polymer photoresists.