The mid-infrared (mid-IR) spectral region contains the characteristic vibrational absorption bands of most molecules as well as two atmospheric transmission windows, and is therefore of critical importance to many biomedical, military, and industrial applications such as spectroscopic sensing, thermal imaging, free-space communications, and infrared countermeasures. Metasurface devices operating in the mid-IR potentially offer significantly reduced size, weight, and cost compared to traditional bulk optics, but they are also challenged with unique material and processing requirements. By combining high-index, broadband transparent dielectric materials with a Huygens metasurface design, we have experimentally realized high-performance metasurface devices with a low-profile, deep sub-wavelength thickness. Based on the platform, we demonstrated single-layer metalenses with focusing efficiencies up to 75% and diffraction-limited performance over a record field of view close to 180 degrees. These meta-optical devices can provide significantly enhanced design flexibility for future infrared optical systems.
The mid-wave infrared (MWIR) is an important band for numerous applications ranging from night vision to biochemical sensing. However, unlike visible or near-infrared (NIR) optical parts, which are economically available off the shelf, MWIR optics are plagued by much higher costs and often inferior performance compared to their visible or NIR counterparts. Optical metasurfaces, artificial materials with subwavelength-scale thicknesses and on-demand electromagnetic responses, provide a promising solution for cost-effective, high-performance infrared optics. Using high-refractive-index (> 5) chalcogenide materials deposited on IR-transparent substrates, we have experimentally demonstrated a MWIR transmissive metasurface device with diffraction-limited focusing and imaging performance and optical efficiency up to 75%. We further show that the metasurface design can accommodate ultra-wide field-of-view and the fabrication method can be extended to conformal integration of metasurface optics on curved surfaces. The projected size, weight and power advantages, coupled with the manufacturing scalability leveraging standard microfabrication technologies, makes the meta-optical devices promising for next-generation MWIR system applications.
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.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.