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Nanopore devices have attracted a lot of attention for their potential application in DNA sequencing. Here, we study how an occluding object placed near a nanopore affects its access resistance by integrating an atomic force microscopy with a nanopore sensor. It is found that there exists a critical hemisphere around the nanopore, inside which the tip of an atomic force microscopy will affect the ionic current. The radius of this hemisphere, which is a bit smaller than the theoretical capture radius of ions, increases linearly with the applied bias voltage and quadratically with the nanopore diameter, but is independent of the operation modes and scanning speeds of the atomic force microscopy. A theoretical model is also proposed to describe how the tip position and geometrical parameters affect the access resistance. [ABSTRACT FROM AUTHOR]

Single-channel 100 GHz and higher bandwidth external optical modulators are dramatically demanded to realize the aggregate carrier data rate of 100 Tb/s per optic-fiber in next-generation optical networks, but the current technologies used in industrial systems have never shown any feasibility to reach such high-speed operations. In this study, the feasible potential of ultrahigh bandwidths higher than 100 GHz are theoretically demonstrated for waveguide electro-optic (EO) modulators with c-axis-oriented BaTiO3 crystal thin-films. As the three dominant factors of determining the bandwidths of EO modulators, the interaction length $L$ , the absolute refractive difference of light-wave and microwave \left| N_m \- N_o \right| determining the velocity mismatch, and the microwave loss coefficient are investigated to realize the ultrahigh bandwidths of over 100 GHz, where L$ is a weight factor of both the velocity mismatch and the microwave loss. Thus, in this process, the nonlinear EO modulation effects are taken into account to determine the L$ values with respect to the values of EO coefficient under a given half-wave voltage V_\pi$ . Then, the optimal tradeoff conditions for the over 100 GHz bandwidths are obtained with the consistent relations among the interaction length, the optical loss, the electrode gap, and the overlap integral of optical and electrical fields, the refractive index difference between the optical guided-mode and the microwave. As a result, for an industrial acceptable V_\pi$ of 5.0 V and a feasible absolute birefringence of 0.005, at the EO coefficient r_{51} values of over 550 pm/V an optimal device in both optical rib waveguide and microwave electrode dimensions shows the illustrative results of over 100 GHz bandwidth in the believable simulations albeit both the velocity mismatch and the microwave loss are taken into account in simulations under a microwave impedance matching, which are all reachable in the real c-axis BaTiO3 crystal thin-film. [ABSTRACT FROM PUBLISHER]

A detailed theoretical study on an optical waveguide biosensor utilizing the modal interference between surface plasmon modes is presented. It is examined that the interaction length i.e. longitudinal dimension of the metallic layer plays a very crucial role in determining the transmission characteristics of such sensors. And as expected, to get a dip in the transmission spectrum around a desired wavelength, the interaction length should be nearly an odd integer multiple of the coupling length corresponding to the surface plasmon modes. It is found that the minimum possible length (equal to one coupling length) of the sensor may not always give the highest figure of merit. Knowing this, we then show that the sensitivity of such a sensor can be further enhanced by optimizing the thicknesses of metal and intermediate layers. [ABSTRACT FROM AUTHOR]

We propose a novel structure for a monolithically integrated parametric frequency up and down converter using two parallel periodically poled lithium niobate (PPLN) waveguides combined with a reflective wavelength-division multiplexer (WDM) to realize second-harmonic-pumped parametric mixing on one chip. The parallel configuration of the PPLN waveguides provides a long interaction length for efficient conversion. The reflective WDM used for (de)multiplexing 0.78- and 1.56-μm light consisted of two multimode interference (MMI) (de)multiplexers and a dichroic mirror. The utilization of the wavelength selectivity of both the MMI (de)multiplexers and the dichroic mirror enabled us to achieve high isolation of the fundamental light for generating a second-harmonic pump. We fabricated the integrated device using a direct-bonded LiNbO3 ridge waveguide. Frequency conversion achieved with two-stage second-harmonic generation and difference frequency generation processes was successfully demonstrated with a high isolation of the fundamental and a parametric gain of the signal in the integrated device. [ABSTRACT FROM PUBLISHER]

Performance limits of saturated parametric amplifiers with very high nonlinear figure of merit were investigated. While such devices can be constructed using high confinement fiber, they also require localized phase matching control over hundreds of meters of interaction length. The limit on signal-induced pump depletion imposed by stochastic dispersion fluctuations in physical fibers is studied for a case of high-gain parametric amplifiers. We show that nanometer-scale fluctuations in fiber transverse geometry can lead to qualitatively different saturation characteristics in very efficient parametric devices. In contrast to a pump-undepleted parametric amplifier, an inhomogeneous parametric amplifier operated in saturation regime is found to possess truly nonreciprocal transfer characteristic. [ABSTRACT FROM PUBLISHER]

In this paper, for the first time, the photorefractive effect in plasmonic waveguides is theoretically modeled and investigated in detail. A metal- LiNbO3-metal nanostructure is considered, with the LiNbO3 being doped with donor and acceptor impurities. The interaction between symmetric and antisymmetric interfering SPP modes is studied. It is shown that a strong symmetric mode can be coupled to a week antisymmetric mode by the mean of photorefractive effect. When the modal losses are taken into account, it was found that losses can limit the interaction length. However, by choosing the proper waveguide length, doping concentration, and amplitude inputs, the photorefractive coupling process is shown yet to be viable despite losses. The coupling effect can be conducted either as an amplification or mode conversion process, promising novel future application. For instant, several known photorefractive applications in microphotonics can be borrowed and implemented in the plasmonic field. [ABSTRACT FROM AUTHOR]

We demonstrate low loss (0.4043 dB/Km at 1.55 μm) deep sub-wavelength broadband evanescent field confinement in low index material from near IR to mid IR wavelengths with the aid of an specialty optical fiber whilst achieving at least 1.5 dB improvement of figure of merit over the previous design. Plane strain analysis has been conducted to foresee fiber material dependent fabrication challenges associated with such nanoscale feature due to thermal stress. Size dependence of air hole is explained rigorously by modifying the existent slot waveguide model. We report significant improvement of field intensity, interaction length, bandwidth and surface sensitivity over the conventional free standing nanowire structure. The effect of metal layer thickness on surface plasmon resonance sensitivity is explored as well. A method to obtain strong evanescent field in such structure for medical sensing is also demonstrated. The proposed technique to enhance sub-wavelength confinement is expected to be of potential engineering merits for optical nanosensors, atomic scale waveguide for single molecule inspection and ultra-low mode volume cavity. [ABSTRACT FROM PUBLISHER]

The coupled thermal reservoir approach described in Part I is demonstrated by analyzing flux and meteorological data covering a range of thermal reservoir conditions. These include mid latitude ocean thermal storage, the surface flux balance of the Pacific warm pool and the land surface flux balance in S. California. In addition to temperature data, the effects of thermal gradients, flux interaction lengths and the time delay or phase shift between the heating flux and the temperature response are considered. Long term climate trends in weather station minimum meteorological surface air temperature (MSAT) data are also analyzed. For selected California and UK weather stations these follow the regional trends in ocean surface temperature. This allows urban heat island effects and other weather station biases to be investigated. The effect of a 100 ppm increase in atmospheric CO2 concentration on these data sets is shown to be too small to be measured. [ABSTRACT FROM AUTHOR]

A dynamic, coupled thermal reservoir description of the Earth's atmospheric energy transfer processes is presented. Solar heat is stored and released by four coupled reservoirs, the land, the oceans and the upper and lower troposphere. In addition to the temperature, there are three other important parameters need to be considered. The first is the thermal gradient, the second is the interaction length and the third is the time delay or phase shift between the incident flux and reservoir thermal response. The Earth's climate is stabilized by the heat stored in these thermal reservoirs, particularly the oceans and the lower troposphere up to 2 km. Almost all of the downward long wave infrared (LWIR) flux reaching the surface originates in the lower troposphere. The dominant energy transfer process within the troposphere is moist convection. At night, the lower troposphere acts as a thermal blanket that slows the surface cooling. The upper troposphere cools continuously by LWIR emission to space. A change in temperature requires a change in the heat stored in the reservoir that has to be calculated using the heat capacity and the time dependent flux balance. The LWIR flux cannot be separated and used to define a change in 'average surface temperature' using blackbody theory. [ABSTRACT FROM AUTHOR]

Abstract: In the present formulation using hydrodynamic model and coupled mode scheme of plasmas the interaction length necessary to achieve optical phase conjugation is obtained from steady-state Brillouin gain coefficient for a semiconductor crystal. The analytical investigation of steady-state gain of stimulated Brillouin scattering (SBS) is made by assuming that the SBS is resulted from the nonlinear interaction of an intense electromagnetic wave with acoustic perturbation internally generated due to acousto-optic property of the semiconductor crystal. Numerical estimates confirm that when cyclotron frequency is tuned with pump frequency, interaction length is found to be nearly smaller than that obtained in absence of magnetic filed. Pump intensity and free carrier concentration both helpful in reducing the required interaction length. [Copyright &y& Elsevier]

Abstract: This paper presents results from an investigation of soot formation in turbulent, non-premixed, C2H4/air jet flames. Tests were conducted using a H2-piloted burner with fuel issuing from a 2.18mm i.d. tube into quiescent ambient air. A range of test conditions was studied using the initial jet velocity (16.2–94.1m/s) as a parameter. Fuel-jet Reynolds numbers ranged from 4000 to 23,200. Planar laser-induced incandescence (LII) was employed to determine soot volume fractions, and laser-induced fluorescence (LIF) was used to measure relative hydroxyl radical (OH) concentrations and polycyclic aromatic hydrocarbons (PAHs) concentrations. Extensive information on the structure of the soot and OH fields was obtained from two-dimensional imaging experiments. Quantitative measurements were obtained by employing the LII and LIF techniques independently. Imaging results for soot, OH, and PAH show the existence of three soot formation/oxidation regions: a rapid soot growth region, in which OH and soot particles lie in distinctly different radial locations; a mixing-dominated region controlled by large-scale motion; and a soot-oxidation region in which the OH and soot fields overlap spatially, resulting in the rapid oxidation of soot particles. Detailed quantitative analyzes of soot volume fractions and OH and soot zone thicknesses were performed along with the temperature measurement using the N2-CARS system. Measurements of OH and soot zone thicknesses show that the soot zone thickness increases linearly with axial distance in the soot formation region, whereas the OH zone thickness is nearly constant in this region. The OH zone thickness then rapidly increases with downstream distance and approximately doubles in the soot-oxidation region. Probability density functions also were obtained for soot volume fractions and OH concentrations. These probability density functions clearly define the spatial relationships among the OH, PAH concentrations, the soot formation, and oxidation processes. [Copyright &y& Elsevier]

A metal-clad optical polarizer with a resonant buffer layer has been investigated by the finite-element method in this paper. Important waveguide design parameters, such as the refractive index, thickness, interaction length, fabrication tolerance, and band-stop characteristics, have been analyzed in detail. Mode coupling within the polarizer and the losses due to coupling between the polarizer and the input and output waveguides are considered using the normal mode analysis. The loss behaviors of and modes are explained and the roles of the resonant buffer layer are interpreted. By using ultralow index layers, resonance, as well as its phase-matching conditions and excellent performance, has also been presented and discussed for this structure for the first time. Simulations show that high performance can be achieved in a wide range of the cladding thicknesses (ges 2 mum) and interaction length for both TE-pass and TM-pass polarizers. With optimized parameters under 3-mm length, it is possible to obtain a broadband TE-pass polarizer with an extinction ratio of more than 40 dB and insertion loss below 0.2 dB over 200 nm, and a TM-pass polarizer with an extinction ratio of more than 30 dB and insertion loss below 0.4 dB over 28 nm. [ABSTRACT FROM PUBLISHER]

Following some general ideas on the discrete kinetic and stochastic game theory proposed by one of the authors in a previous work, this paper develops a discrete velocity mathematical model for vehicular traffic along a one-way road. The kinetic scale is chosen because, unlike the macroscopic one, it allows to capture the probabilistic essence of the interactions among the vehicles, and offers at the same time, unlike the microscopic one, the opportunity of a profitable analytical investigation of the relevant global features of the system. The discretization of the velocity variable, rather than being a pure mathematical technicality, plays a role in including the intrinsic granular nature of the flow of vehicles in the mathematical theory of traffic. Other important characteristics of the model concern the gain and loss terms of the kinetic equations, namely the construction of a density-dependent table of games to model velocity transitions and the introduction of a visibility length to account for nonlocal interactions among the vehicles. [ABSTRACT FROM AUTHOR]

In this paper, we present a detailed analysis about the relationship of half-wave voltage ( V π ) and bandwidth (Δ f ), based on a full vectorial finite difference (FVFD) mode solver for an optical waveguide and a finite-element method (FEM) for a microwave electrode, of an electro-optic (EO) polymer modulator. It has been found that we can get desirable V π L and Δ fL ( L is EO interaction length) simultaneously. In other words, only the interaction length should be considered for a tradeoff of the V π and Δ f in the design of a polymer EO modulator. [ABSTRACT FROM AUTHOR]

We demonstrate a narrow-bandwidth acoustooptic tunable filter with very low polarization-sensitivity using a dispersion-compensating fiber that has a large group index difference between the core and the cladding modes with a specific stress distribution. The 3-dB bandwidth of the filter is 0.8 nm with the interaction length of 10 cm, and the polarization-dependent center-wavelength splitting is 0.04 nm at the wavelength around 1550 nm. The origin of the low polarization-dependence is successfully explained through the analysis on the stress field in the fiber. [ABSTRACT FROM PUBLISHER]

We report the use of a single-mode tapered fiber coated with a dispersive material as a tunable band-edge filter. The band-edge wavelength can be adjusted, over a range of ∼500 nm (1150-1650 nm), in a simple way with the taper waist diameter, the interaction length, or with the refractive index of the dispersive material that coats the taper. Moreover, the fabrication procedure is simple and of low cost. [ABSTRACT FROM PUBLISHER]

Quasi-phase-matched difference frequency generation devices for the 1.5-μm band using a LiNbO3 waveguide with a high-index cladding layer of As2S3 were designed and fabricated. By the cladding, the guided mode profiles were modified, and their overlap was increased. A high normalized conversion efficiency of 790%/W was obtained for 30-mm interaction length. [ABSTRACT FROM PUBLISHER]

Polymeric APC-CPW electrooptic modulators incorporating an inverted-rib waveguide structure were fabricated and tested for the first time. The inverted structure greatly simplifies fabrication procedures, and additionally improves propagation loss performance. Mach-Zehnder electrooptic modulators fabricated using this structure exhibited 6 dB of fiber-to-fiber insertion loss for 2.3-cm length and 6 V of driving voltage for a one-arm micro-strip electrode of 1.5-cm interaction length, at a wavelength of 1.55 μm. [ABSTRACT FROM PUBLISHER]