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When light-matter polaritons travel in periodic media, they acquire properties akin to Bloch quasi-particles in crystals., Efficient control of photons is enabled by hybridizing light with matter. The resulting light-matter quasi-particles can be readily programmed by manipulating either their photonic or matter constituents. Here, we hybridized infrared photons with graphene Dirac electrons to form surface plasmon polaritons (SPPs) and uncovered a previously unexplored means to control SPPs in structures with periodically modulated carrier density. In these periodic structures, common SPPs with continuous dispersion are transformed into Bloch polaritons with attendant discrete bands separated by bandgaps. We explored directional Bloch polaritons and steered their propagation by dialing the proper gate voltage. Fourier analysis of the near-field images corroborates that this on-demand nano-optics functionality is rooted in the polaritonic band structure. Our programmable polaritonic platform paves the way for the much-sought benefits of on-the-chip photonic circuits.

Four spinful photonic C6 photonic higher-order topological insulators are investigated. We show that two are robust to spin-orbit coupling while two are not. We derive a new invariant to predict this effect on corner states.

Ultrastrong confinement, long lifetime, and gate-tunability of graphene plasmon polaritons (GPPs) motivate wide-ranging efforts to develop GPP-based active nanophotonic platforms. Incorporation of topological phenomena into such platforms will ensure their robustness as well as enrich their capabilities as promising test beds of strong light–matter interactions. A recently reported approach suggests an experimentally viable platform for topological graphene plasmonics by introducing nanopatterned gates—metagates. We propose a metagate-tuned GPP platform emulating a second-order topological crystalline insulator. The metagate imprints its crystalline symmetry onto graphene by modulating its chemical potential via field-effect gating. Depending on the gate geometry and applied voltage, the resulting two-dimensional crystal supports either one-dimensional chiral edge states or zero-dimensional midgap corner states. The proposed approach to achieving the hierarchy of nontrivial topological invariants at all dimensions lower than the dimension of the host material paves the way to utilizing higher-order topological effects for on-chip and ultracompact nanophotonic waveguides and cavities.

To measure object wave in digital holography, the phase-shifting technique is popular by changing the phase of the reference wave. A piezo actuator (PZT) is usually used as a device to shift the phase. In a case to obtain the phase information of color object with multiple wavelengths, four-step phase-shifting algorithm with quarter wavelength shift is not convenient since the amount of the phase shift is difference according to each wavelength. In this paper, the generalized four-step phase-shifting method is proposed and experimentally verified to obtain color digital hologram using an image sensor with a Bayer pattern for capturing interference pattern shifted phase by one PZT.

Polarization is one of the important properties of light, and its detection is of significant interest for various fundamental and practical applications. We demonstrate a mid-infrared polarimetry device using a gate-tunable graphene-integrated anisotropic metasurface. The Stokes parameters of the incident light are extracted by sweeping the gate voltage applied to the device and subsequent fitting of the measured reflected intensities. Considering subpicosecond carrier relaxation times in graphene, the polarization measurement rate of our device is governed only by the speed of the gate voltage sweep. Thus, our work serves as a proof-of-principle demonstration for high-speed microscale polarimetric devices.

Photonic crystals are commonly implemented in media with periodically varying optical properties. Photonic crystals enable exquisite control of light propagation in integrated optical circuits, and also emulate advanced physical concepts. However, common photonic crystals are unfit for in-operando on/off controls. We overcome this limitation and demonstrate a broadly tunable two-dimensional photonic crystal for surface plasmon polaritons. Our platform consists of a continuous graphene monolayer integrated in a back-gated platform with nano-structured gate insulators. Infrared nano-imaging reveals the formation of a photonic bandgap and strong modulation of the local plasmonic density of states that can be turned on/off or gradually tuned by the applied gate voltage. We also implement an artificial domain wall which supports highly confined one-dimensional plasmonic modes. Our electrostatically-tunable photonic crystals are derived from standard metal oxide semiconductor field effect transistor technology and pave a way for practical on-chip light manipulation., Traditional photonic crystals consist of periodic media with a pre-defined optical response. Here, the authors combine nanostructured back-gate insulators with a continuous layer of graphene to demonstrate an electrically tunable two-dimensional photonic crystal suitable for controlling the propagation of surface plasmon polaritons.

Topological photonics offers remarkable solutions to robust light propagation and coupling. Two challenges can be identified: (1) making topological structures reconfigurable, and (2) shrinking them to nanoscale. I will discuss a platform that addresses both challenges: a valley plasmonic crystal for graphene surface plasmons. We demonstrate that a designer metagate, placed within a few nanometers of graphene, can be used to impose a periodic Fermi energy landscape on graphene. For specific metagate geometries and bias voltages, the combined metagategraphene structure is shown to produce complete propagation band gaps for the plasmons, and to impart them with nontrivial valley-linked topological properties. Sharply curved domain walls between differently patterned metagates are shown to guide highly localized plasmons without any reflections owing to suppressed intervalley scattering.

In this study, cylindrical diffusing optical fiber probe (CDOFP) used for tumor treatment using PDT method is developed and analyzed. Diffusing beam profile of 5mm to 40mm tip length probe is produced and analyzed using laser scribing equipment developed in a previous research. Ball tip at the tip of CDOFP was developed for easier infiltration of tissues and the beam profile of such tip is reviewed. Additionally, CDOFP for PDT tumor treatment was used for laser coagulation test on animal tissue. CDOFP with diffusing tip length 5mm and 15mm was infiltrated inside a cow's liver tissue to process laser coagulation test. Coagulation and thermal damage was measured with twice the maximum intensity of laser, where maximum intensity in-vivo test is 1W 200J.

Color digital holography (DH) has been researched in various fields such as the holographic camera and holographic microscope because it acquires a realistic color object wave by measuring both amplitude and phase. Among the methods for color DH, the phase-shifting DH has an advantage of obtaining a signal wave of objects without the autocorrelation and conjugate noises. However, this method usually requires many interferograms to obtain signals for all wavelengths. In addition, the phase-shift algorithm is sensitive to the phase-shift error caused by the instability or hysteresis of the phase shifter. In this paper, we propose a new method of color phase-shifting digital holography with monitoring the phase-shift. The color interferograms are recorded by using a focal plane array (FPA) with a Bayer color filter. In order to obtain the color signal wave from the interferograms with unexpected phase-shift values, we devise a generalized phase-shifting DH algorithm. The proposed method enables the robust measurement in the interferograms. Experimentally, we demonstrate the proposed algorithm to reconstruct the object image with negligibly small conjugate noises.

Internet of Things (IoT) becomes an inevitable technology for ICT convergence. It gathers information from various objects and provides intelligent services through analyzing the information. To collect surrounding information, IoT employs a sensor network, which is a low-power wireless communication network with numerous sensor nodes. Sensor nodes in conventional sensor networks have short transmission range. However, it is required a sensor network with long transmission range as well as low transmission power consumption for various IoT services. Long transmission range of IoT devices affects transmission environment. Lots of sensor nodes (i.e., IoT devices) in the long range sensor network transmit data to a given gateway node in order to deliver data to a network server. The gateway node can experience serious traffic load to relay the data. It causes to drop transmission efficiency. Therefore, for efficient data transmission, a network architecture and a data transmission method for long range IoT services are necessary. This paper proposes the network and data transmission architecture for the long range sensor networks. The proposed network architecture is based on oneM2M IoT standard. It has Infrastructure Node (IN), Middle Node (MN) and Application Service Node (ASN) as network elements. In the proposed method, IN employs cloned MNs to reduce the traffic load at the MN, which is the gateway. ASN delivers data through MN or cloned MNs to the IN. Through the load balancing by the proposed method at the MN, the efficient data transmission for IoT services in long range sensor networks can be provided. The performance of the proposed method is validated by the computer simulation.

A valley plasmonic crystal for graphene surface plasmons is proposed. We demonstrate that a designer metagate, placed within a few nanometers of graphene, can be used to impose a periodic Fermi energy landscape on graphene. For specific metagate geometries and bias voltages, the combined metagate-graphene structure is shown to produce complete propagation band gaps for the plasmons, and to impart them with nontrivial valley-linked topological properties. Sharply curved domain walls between differently patterned metagates are shown to guide highly localized plasmons without any reflections owing to suppressed intervalley scattering. Our approach paves the way for nonmagnetic and dynamically reconfigurable topological nanophotonic devices.

This paper proposes the development of cylindrical diffusing optical fiber probe (CDOFP), which possesses a flexible structure and solidity apt to treat cancer during photo-dynamic therapy (PDT). The cylindrical diffusing tip of CDOFP is made from a laser processing system with homogeneity and precision. We fabricated and characterized CDOFP to investigate its clinical feasibility and other possible applications of light therapy using the diffusing optical fiber.

We synthesized a solution-processable low band gap small molecule, Si1TDPP-EE-COC6, for use as a semiconducting channel material in organic thin film transistors (OTFTs). The Si1TDPP-EE-COC6 is composed of electron-rich thiophene–dithienosilole–thiophene (Si1T) units and electron-deficient diketopyrrolopyrrole (DPP) and carbonyl units. SiTDPP-EE-COC6-based OTFTs with Au source/drain electrodes were fabricated, and their electrical properties were systematically investigated with increasing thermal annealing temperature. The hole and electron mobilities of as-spun Si1TDPP-EE-COC6 were 3.3 × 10–4 and 1.7 × 10–4 cm2 V–1 s–1, respectively. The carrier mobilities increased significantly upon thermal annealing at 150 °C, yielding a hole mobility of 0.003 cm2 V–1 s–1 and an electron mobility of 0.002 cm2 V–1 s–1. The performance enhancement upon thermal annealing was strongly associated with the formation of a layered edge-on structure and a reduction in the π–π intermolecular spacing. Importantly, the use of at...

We have demonstrated polarimetry using an anisotropic metasurface on gate-tunable monolayer graphene as an electro-optic modulator. Operating by electric gate-tuning, our device measures polarization ellipse of mid-infrared light and successfully distinguishes two circular polarization states.

We propose a electrically tunable plasmonic platform for valleytronics—a mono-layer graphene with its chemical potential controlled by a periodically structured metagate. Topologically protected edge states show reflection-free propagation around sharp corners.

The Wireless Body Area Network (WBAN) that can collect measured vital signs through sensors enables continuous monitoring of the elder and of chronic diseases. As smart devices become popular, development of the WBAN becomes easier. Our research implemented an integration platform that consists of WBAN and cloud computing based on the Transmission Control Protocol (TCP). We optimized the WBAN and the TCP as a sampling rate control. A sampling rate is the number of transfer data per second. The sampling rate is an important factor in the resolution of waveforms, though high sampling rates can cause a decline in network performance. A smart device performs three threads, such as Bluetooth, main, and TCP. The Bluetooth thread was implemented to collect vital signs from sensing nodes. The main thread performs computations for drawing waveforms and transmits data to the TCP thread. The TCP thread transmits vital signs to a server. We verified our proposed integration platform with formal verification and simulation. We expect to contribute to the platform development of WBAN and to cloud computing.

We characterized the electrical properties of a field-effect transistor (FET) and a nonvolatile memory device based on a solution-processable low bandgap small molecule, Si1TDPP-EE-C6. The small molecule consisted of electron-rich thiophene-dithienosilole-thiophene (Si1T) units and electron-deficient diketopyrrolopyrrole (DPP) units. The as-spun Si1TDPP-EE-C6 FET device exhibited ambipolar transport properties with a hole mobility of 7.3×10(-5) cm2/(Vs) and an electron mobility of 1.6×10(-5) cm2/(Vs). Thermal annealing at 110 °C led to a significant increase in carrier mobility, with hole and electron mobilities of 3.7×10(-3) and 5.1×10(-4) cm2/(Vs), respectively. This improvement is strongly correlated with the increased film crystallinity and reduced π-π intermolecular stacking distance upon thermal annealing, revealed by grazing incidence X-ray diffraction (GIXD) and atomic force microscopy (AFM) measurements. In addition, nonvolatile memory devices based on Si1TDPP-EE-C6 were successfully fabricated by incorporating Au nanoparticles (AuNPs) as charge trapping sites at the interface between the silicon oxide (SiO2) and cross-linked poly(4-vinylphenol) (cPVP) dielectrics. The device exhibited reliable nonvolatile memory characteristics, including a wide memory window of 98 V, a high on/off-current ratio of 1×10(3), and good electrical reliability. Overall, we demonstrate that donor-acceptor-type small molecules are a potentially important class of materials for ambipolar FETs and nonvolatile memory applications.

In this paper, the adoption of the full-duplex radio (FDR) technique in three-node decode-and-forward (DF) relaying systems, which consist of a transmit node, a relay node and a destination node, is considered. In particular, in handling the self-interference the effect of the distortion noise due to the limited dynamic range of the analog-to-digital converter (ADC) is considered which may limit the potential of FDR. We first analyze the closed-form analytical expression of the system outage performance and then, derive the optimal transmit power of the relay to minimize the outage probability. Through extensive numerical results, we investigate that the full-duplex relaying can outperform the conventional half-duplex relaying significantly. Numerical results also indicate that although self-interference may reduce the system performance, the outage probability can be efficiently controlled by choosing a suitable relay transmit power.

The WBAN that can collect measured vital sign through sensors enables continuous monitoring for the elder and chronic disease. As smart devices become popular, the development of WBAN has been easier. We have optimized WBAN by control of sampling rate. The sampling rate presents as the number of data per second. It is important factor that determines resolution of waveform. Even high sampling rate cause decline of network performance. The smart device has multi threads such as Bluetooth thread and main thread. The Bluetooth thread collects vital sign from sensing node. The main thread performs processing for vital sign and computation for drawing waveform. We expect to contribute to developing of cloud computing system for u-Health environment.

As aging population increases, the demand of medical systems for elder and chronic disease is also increasing. Our research evaluates on performance of TCP/UDP in order to assist cloud computing. We optimize communication between smart device and server using TCP. The sampling rate presents the number of data per second. The sampling rate is important factor in resolution of waveform, though high sampling rate causes decline of network performance. The smart device performs three threads such as Bluetooth, main, TCP/UDP. The Bluetooth thread collects vital sign from sensing node. The main thread performs computation for drawing waveform and transmits data to TCP/UDP thread. The TCP/UDP thread transmits vital sign to server. We expect to contribute to development of WBAN and cloud computing.

Recently ubiquitous health which can monitor individual health condition always and everywhere is being researched. The elderly and the chronic disease can have their own personal healthcare devices and they can monitor themselves easily. But some kind of limitation is still remaining in their life even if they have powerful smart devices. They need to go to get treatment and to prepare medicine but automotive system does not support interfaces for personal healthcare devices. We consider performance of Bluetooth in order to build efficient network that consist of compliant IEEE 11073 medical devices in automotive environment. Also, to manage efficient automotive, interconnection between IVN and smart device is considered.

u-Health care requires interoperability between medical devices. IEEE 11073 is an internationally harmonized family of standards, produced by a grouping of manufacturers, institutions and IEEE Institute. It ensures interoperability between medical devices in u-Health environment. The Bluetooth is used for communication. We focus on new and innovative NFC based Bluetooth pairing in u-Health environment. It can enhance the user experience of applications that use the Bluetooth technology. The enhancements can be select a Bluetooth device, securely connect to a Bluetooth device, start an application on a Bluetooth device.