36 research outputs found

    Visualization 1.mp4

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    tuning proces

    2: One-way surface magnetoplasmon cavity and its application for nonreciprocal devices

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    Originally published in Optics Letters on 15 February 2016 (ol-41-4-800

    1: One-way surface magnetoplasmon cavity and its application for nonreciprocal devices

    No full text
    Originally published in Optics Letters on 15 February 2016 (ol-41-4-800

    High-Performance Self-Powered Transparent Metal–Semiconductor-Metal Ultraviolet Photodetector Based on Sub-10 nm Thick Dual-Asymmetric Interdigitated Electrodes

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    Transparent self-powered ultraviolet (UV) photodetectors (PDs) are demonstrated experimentally with dual-asymmetric interdigitated electrodes composed of Au and Ag with different sizes on top of a ZnO active layer. The electrodes are sub-10 nm thick and highly transparent in both UV and visible regimes, making the whole device look transparent and output light current over 1/3 higher than that of the counterpart with thick opaque electrodes at 0 V. The PD with only electrode material asymmetry can work at 0 V because of the Schottky junction formed at the Au/ZnO interface and the Ohmic contact at the Ag/ZnO interface. The junction asymmetry can be further enhanced by the electrode size difference. The PD with a Au and Ag finger width ratio of 1:4 achieves a photocurrent over 11 times that of the device with identical Au and Ag sizes. A high responsivity of 56.3 μA/W and a high detectivity of 1.54 × 108 Jones are achieved. The rise and fall times are as low as 3.1 and 2.8 ms, respectively. By patterning the pads, our PD becomes more uniform and transparent with an average visible transmissivity improved to 77.6% (the highest among the UV PD chips reported), while the optoelectronic conversion performance remains unchanged. The overall properties are comparable and even superior to those of the previously reported counterparts. This work provides insights into the design and mechanism of transparent self-powered UV PDs, facilitating advancements in this field

    Local and Nonlocal Optically Induced Transparency Effects in Graphene–Silicon Hybrid Nanophotonic Integrated Circuits

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    Graphene is well-known as a two-dimensional sheet of carbon atoms arrayed in a honeycomb structure. It has some unique and fascinating properties, which are useful for realizing many optoelectronic devices and applications, including transistors, photodetectors, solar cells, and modulators. To enhance light–graphene interactions and take advantage of its properties, a promising approach is to combine a graphene sheet with optical waveguides, such as silicon nanophotonic wires considered in this paper. Here we report <i>local</i> and <i>nonlocal</i> optically induced transparency (OIT) effects in graphene–silicon hybrid nanophotonic integrated circuits. A low-power, continuous-wave laser is used as the pump light, and the power required for producing the OIT effect is as low as ∼0.1 mW. The corresponding power density is several orders lower than that needed for the previously reported saturated absorption effect in graphene, which implies a mechanism involving light absorption by the silicon and photocarrier transport through the silicon–graphene junction. The present OIT effect enables low power, all-optical, broadband control and sensing, modulation and switching <i>locally</i> and <i>nonlocally</i>

    ROS and p53 involve in cytochrome <i>c</i>-mediated caspase-3 activation during 1800MHz microwave-induced cell apoptosis.

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    <p>(A, B) Effects of NAC, PIF-α, Ac-DEVD-CHO and Z-VAD-FMK on cell viability and caspase-3 activity after 1800MHz microwave radiation for 24 hours in NIH/3T3 and U-87 MG cells. Cells were pretreated with treatments (NAC, PIF-α, Ac-DEVD-CHO and Z-VAD-FMK) for 20 min and then exposed to 1800MHz microwave or sham treatment for 24 hours. After microwave radiation, cells were harvested and levels of cell viability and caspase-3 activity were measured in NIH/3T3 and U-87 MG cells. Cell Counting Kit-8 (CCK-8, Dojindo Laboratories, Kumamoto, Japan) was used to evaluate cell viability after various treatments. Caspase-3 activity was measured by the caspase-3 activity kit. (C, D) Western blotting analysis of caspase-3 activation and cytochrome <i>c</i> release from mitochondria to cytoplasm. Cells were pretreated with or without NAC and PIF-α for 20 min before exposure to 1800MHz microwave. After microwave radiation for 24 hours, cells were harvested and measured protein levels of caspase-3. The cytoplasm proteins were extracted using a mitochondria/cytoplasm fractionation kit followed by western blotting analysis of cytochrome <i>c</i> in cytoplasm. MW, microwave; NAC, N-acetyl-L-cysteine. PIF-α, pifithrin-α. All the data in these figures are presented as mean ± S.D. (n = 3; *P < 0.05 vs. control group; #P < 0.05 indicated group.)</p

    1800MHz Microwave Induces p53 and p53-Mediated Caspase-3 Activation Leading to Cell Apoptosis <i>In Vitro</i>

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    <div><p>Recent studies have reported that exposure of mammalian cells to microwave radiation may have adverse effects such as induction of cell apoptosis. However, the molecular mechanisms underlying microwave induced mammalian cell apoptosis are not fully understood. Here, we report a novel mechanism: exposure to 1800MHz microwave radiation induces p53-dependent cell apoptosis through cytochrome <i>c</i>-mediated caspase-3 activation pathway. We first measured intensity of microwave radiation from several electronic devices with an irradiation detector. Mouse NIH/3T3 and human U-87 MG cells were then used as receivers of 1800MHz electromagnetic radiation (EMR) at a power density of 1209 mW/m<sup>2</sup>. Following EMR exposure, cells were analyzed for viability, intracellular reactive oxygen species (ROS) generation, DNA damage, p53 expression, and caspase-3 activity. Our analysis revealed that EMR exposure significantly decreased viability of NIH/3T3 and U-87 MG cells, and increased caspase-3 activity. ROS burst was observed at 6 h and 48 h in NIH/3T3 cells, while at 3 h in U-87 MG cells. Hoechst 33258 staining and in situ TUNEL assay detected that EMR exposure increased DNA damage, which was significantly restrained in the presence of N-acetyl-L-cysteine (NAC, an antioxidant). Moreover, EMR exposure increased the levels of p53 protein and p53 target gene expression, promoted cytochrome <i>c</i> release from mitochondrion, and increased caspase-3 activity. These events were inhibited by pretreatment with NAC, pifithrin-α (a p53 inhibitor) and caspase inhibitor. Collectively, our findings demonstrate, for the first time, that 1800MHz EMR induces apoptosis-related events such as ROS burst and more oxidative DNA damage, which in turn promote p53-dependent caspase-3 activation through release of cytochrome <i>c</i> from mitochondrion. These findings thus provide new insights into physiological mechanisms underlying microwave-induced cell apoptosis.</p></div

    Broadband High-Efficiency Half-Wave Plate: A Supercell-Based Plasmonic Metasurface Approach

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    We design, fabricate, and experimentally demonstrate an ultrathin, broadband half-wave plate in the near-infrared range using a plasmonic metasurface. The simulated results show that the linear polarization conversion efficiency is over 97% with over 90% reflectance across an 800 nm bandwidth. Moreover, simulated and experimental results indicate that such broadband and high-efficiency performance is also sustained over a wide range of incident angles. To further obtain a background-free half-wave plate, we arrange such a plate as a periodic array of integrated supercells made of several plasmonic antennas with high linear polarization conversion efficiency, consequently achieving a reflection-phase gradient for the cross-polarized beam. In this design, the anomalous (cross-polarized) and the normal (copolarized) reflected beams become spatially separated, hence enabling highly efficient and robust, background-free polarization conversion along with broadband operation. Our results provide strategies for creating compact, integrated, and high-performance plasmonic circuits and devices
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