Bulletin of the American Physical Society
Joint Fall 2017 Meeting of the Texas Section of the APS, Texas Section of the AAPT, and Zone 13 of the Society of Physics Students
Volume 62, Number 16
Friday–Saturday, October 20–21, 2017; The University of Texas at Dallas, Richardson, Texas
Session E6: Optics II |
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Chair: Alex Zakhidov, Texas State Univ. San Marcos Room: DGAC 1.135 |
Friday, October 20, 2017 4:15PM - 4:27PM |
E6.00001: Tunable conducting oxide metasurface color filter Jinqiannan Zhang, Long Tao, Aleksei Anopchenko, Ho Wai Howard Lee Optoelectronic transducing mechanism provides an unprecedented opportunity to achieve post-fabrication control in metasurface devices. However, there are only few works on electrically controlled metasurface color filters. In this work, we propose a novel color filter structure in which the light transmission can be electrically controlled. The proposed structure is a modified periodic metal-insulator-metal (MIM) configuration with ultrathin layers of indium tin oxide (ITO) and hafnium dioxide (HfO$_{\mathrm{2}})$ sandwiched between two gold nanostrips. When electrically biased the ITO layer changes its optical property due to the electron accumulation at the ITO-HfO$_{\mathrm{2}}$ interface and hence changes dispersion property of the structure. The numerical simulation shows that a high electrical modulation ratio of 20.5 dB of transmission can be achieved around the frequency region where ITO's permittivity is close to zero, known as the epsilon-near-zero (ENZ) point. Moreover, the structure exhibits the maximum resonance shift of 40 nm under the electrical bias of 5 V. The electrical modulated nanoscale color filter can be used in imaging devices and bring new functionalities to cameras or biosensing. [Preview Abstract] |
Friday, October 20, 2017 4:27PM - 4:39PM |
E6.00002: Reflective photonic limiter based on a phase-changing material Rodion Kononchuk, Andrey Chabanov, Martin Hilario, Benmaas Jawdat, Brad Hoff, Vladimir Vasilyev, Nicholaos Limberopoulos, Ilya Vitebskiy Optical limiters protect the human eye and sensitive optical devices from laser-induced damage. The existing limiters utilize nonlinear optical materials which transmit low-intensity light, while blocking the laser radiation with intensity exceeding a certain limiting threshold. The limiting threshold is determined by nonlinear absorption and, in many cases, is much higher than the practically required value. An additional problem with the existing limiters is that the laser-induced damage threshold of the nonlinear material is usually close to the limiting threshold, in which case the limiter itself can be irreversibly damaged if engaged. To address the above problems, we have developed a reflective limiter in which the phase-change material, VO2, is incorporated in a photonic structure with engineered dispersion. At low intensities, the photonic structure displays a strong resonant transmission. Above the limiting threshold, VO2 undergoes a heat-induced transition to the metallic phase to render the photonic structure highly reflective, which prevents it from overheating and destruction. Such a photonic limiter has significantly lower limiting threshold and much higher damage threshold compared to VO2 itself. The photonic limiter is going to be tested with millimeter waves. [Preview Abstract] |
Friday, October 20, 2017 4:39PM - 4:51PM |
E6.00003: Gate-tunable electromagnetically-induced transparency plasmonic modulator Long Tao, Aleksei Anopchenko, Jinqiannan Zhang, Sudip Gurung, Ho Wai Howard Lee Plasmonic components show promising properties in building interconnects for future photonic and electronic hybrid circuits due to their nanoscale footprints and high optical bandwidth. Along with this idea, we demonstrate an electrically tunable ultracompact plasmonic modulator. To enhance modulation strength, we use the electromagnetically-induced transparency configuration. The modulator is a metal-oxide-semiconductor (MOS) slot waveguide structure consisting of two stubs on the same side of bus waveguide forming a coupled system. Heavily n-doped indium tin oxide (ITO) is used as the semiconductor in MOS waveguide. By electrically biasing the MOS structure, we show a modulator with large modulation strength (more than 10 dB/$\mu $m), low waveguide loss (less than 1 dB/$\mu $m), and a small footprint. The large modulation strength can be explained by the formation of the epsilon-near-zero layer at the ITO-oxide interface at the wavelength of the modulated signal. Numerical simulation results reveal that such a significant modulation can be achieved with a small voltage (3 V). This result shows promise in developing nanoscale modulators for future compact photonic integrated circuits. [Preview Abstract] |
Friday, October 20, 2017 4:51PM - 5:03PM |
E6.00004: Field-Effect Tunable Epsilon-Near-Zero Perfect Absorption. Aleksei Anopchenko, Long Tao, Catherine Arndt, Ho Wai Howard Lee High efficient light absorbers are in demand for light harvesting, high-resolution, and optical coating technologies. Recent studies suggest that zero-index or epsilon-near-zero (ENZ) materials can be used in making ultrathin perfect absorbers. Indium tin oxide (ITO) with electron concentration controllable over a broad range of 5\texttimes 10$^{\mathrm{20}}$-2\texttimes 10$^{\mathrm{21}}$ cm$^{\mathrm{-3}}$ shows ENZ in the near-IR region of 700 nm -1.8~$\mu $m. The ultrathin layers of ITO support certain plasmonic modes at ENZ frequencies. Excitation of these modes leads to resonant light absorption with 100{\%} efficiency. In this talk, we show, for the first time, post-fabrication tuning of the ENZ perfect absorption in ITO thin film. We will discuss perfect absorption in deep subwavelength ($\lambda $/100) ITO nanolayers due to the excitation of the bound and radiative ENZ modes. The nanolayer thickness required for the mode critical coupling and perfect absorption is computed for each ENZ mode and used to evaluate the optimal thickness for the perfect absorption tuning. The resonant absorption wavelength is tunable via the field-effect in a metal-oxide-semiconductor (MOS) capacitor. The direct tuning of the perfect absorption is possible due to the subwavelength thickness (\textless 8 nm) of the ENZ perfect absorber - comparable to the Debye length (\textasciitilde 1 nm) of the electron accumulation region. The post-fabrication tuning of about 20{\%} of perfect absorption with respect to the full width at half maximum of the absorption peak is achieved for the devices under study. [Preview Abstract] |
Friday, October 20, 2017 5:03PM - 5:15PM |
E6.00005: Origins and Applications of the Optical Properties of Graphene Derivatives Anton Naumov, Md. Tanvir Hasan, Elizabeth Sizemore, Conor Ryan, Thomas Paz Due to its remarkable properties, graphene has become a basis of many novel microelectronic devices. However its functional derivatives including graphene oxide (GO) can be mass-produced at lower costs and retain many properties of graphene in addition being water soluble. GO also exhibits fluorescence in the visible/near-IR suitable for applications in optoelectronics and biomedicine. We aim to explain optical properties of GO and other novel graphene derivatives produced in our work as a result of confinement of graphitic domains by functional groups. Functionalization-induced changes in emission signatures of GO together with appearance of fluorescence after nitration or bromination of initially non-emissive reduced graphene oxide support this confinement-induced band gap model. Additionally we show that optical properties of GO can be utilized for in-vitro molecular imaging and pH-sensing in cancer and healthy cells. GO flakes optimized for this application are non-toxic at imaging concentrations and exhibit efficient internalization at 1h post transfection as they are imaged in the cytoplasm. As a result this work elucidates the origins of optical properties of graphene derivatives and explores their applications in nanomedicine. [Preview Abstract] |
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