We studied the influence of nanosteps on signal intensity in gap-mode tip-enhanced Raman spectroscopy (TERS). A benzenethiol monolayer adsorbed an Au substrate was investigated. The correlation between TERS and local topography shows that a 2 nm high sharp step surface can significantly increase enhancement. Furthermore, theoretical models were built, numerical simulation results consistent with our experimental results. findings provide evidence nanoscale roughness play crucial role "hot...

Abstract Biosensing with nanoholes is one of the most promising applications nanoplasmonic devices. The sensor properties, however, are complex due to coupled resonances through propagating and localized surface plasmons. This Full Paper demonstrates experimental simulation studies on different plasmonic hole systems, namely various patterns circular holes in gold films. In contrast previous work, here, challenging situation optically thin films considered. refractive‐index‐sensing such as...

Energy distribution curves of laser-induced electron pulses from a tungsten tip have been measured as function voltage and laser power. Electron emission via tunneling through and/or excitation over the surface barrier photoexcited nonequilibrium distributions are clearly observed. The spectral shapes largely vary with processes strongly affected by dynamics. Simulations successfully reproduce spectra, thus allowing direct insight into involved dynamics revealing temporal tunability two...

Plasmonic memristors are electrically activated optical switches with a memory effect. This effect is important for new generation of latching that maintain their state without power consumption. It also interest memories can be by single electrical write/erase impulse. The operation principle based on the reversible formation conductive path in dielectric layer plasmonic metal–insulator–metal waveguide. Extinction ratios 12 dB (6 dB) demonstrated 10 μm (5 μm) long devices operating voltages...

To optimize the interaction between chiral matter and highly twisted light, quantities that can help characterize electromagnetic fields near nanostructures are needed. Here, by analogy with Poynting's theorem, we formulate time-averaged conservation law of optical chirality in lossy dispersive media identify flux as an ideal far-field observable for characterizing fields. Bounded law, show it provides precise information, unavailable from circular dichroism spectroscopy, on magnitude...

We have investigated field-emission patterns from a clean tungsten tip apex induced by femtosecond laser pulses. Strongly asymmetric modulations of the intensity distributions are observed depending on polarization light and incidence direction relative to azimuthal orientation apex. In effect, we realized an ultrafast pulsed source with site selectivity. Simulations local fields electron emission based photoexcited nonequilibrium explain our observations quantitatively.

We report on high-extinction-ratio, ultrafast plasmonic Mach-Zehnder modulators. demonstrate data modulation at line rates up to 72 Gbit/s (BPSK) and 108 (4-ASK). The driving voltages are U <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">d</sub> = 4 2.5 V xmlns:xlink="http://www.w3.org/1999/xlink">p</sub> for 12.5 25 μm short devices, respectively. frequency response shows no bandwidth limitations 70 GHz. Static characterizations indicate...

A method for the computation of band structure two-dimensional photonic crystals is presented. It well suited including materials with arbitrary frequency-dependent dielectric constants. The technique can be applied to study irregularly shaped (noncircular) elements. This based on multiple multipole method. In order find solutions nonlinear eigenvalue problem, a multipolar source introduced which acts as an excitation. By varying frequency source, various eigenmodes are excited and localized...

We investigate the optical forces acting on a metallic nanoparticle when is introduced within photonic nanojet (PNJ). Optical at resonance and off-resonance conditions of microcylinder or are investigated. Under proper polarization conditions, whispering gallery mode can be excited in microcylinder, even off provided that scattering from strong enough. The enhanced either single with respect to under off-resonant illuminations. found depend strongly dielectric permittivity nanoparticle, as...

Plasmonic nano antennas are highly attractive at optical frequencies due to their strong resonances - even when size is smaller than the wavelength and because of potential extreme field enhancement. Such may be applied for sensing biological particles as well single molecule detection. Because considerable material losses dispersion metals frequencies, numerical analysis plasmonic very demanding. An additional difficulty caused narrow gaps between utilized increasing In this paper we...

Abstract Illuminating a nano-sized metallic tip with ultrashort laser pulses leads to the emission of electrons due multiphoton excitations. As optical fields become stronger, tunnelling directly from Fermi level becomes prevalent. This can generate coherent electron waves in vacuum leading variety attosecond phenomena. Working at high currents where multi-electron effects are significant, we were able characterize transition one regime other. Specifically, found that onset laser-driven is...

Field-emission patterns from a clean tungsten tip apex induced by femtosecond laser pulses have been investigated. Strongly asymmetric field-emission intensity distributions are observed depending on three parameters: (1) the polarization of light, (2) azimuthal and (3) polar orientation relative to incidence direction. In effect, we realized an ultrafast pulsed source with site selectivity few tens nanometers. Simulations local fields electron emission based photo-excited nonequilibrium...

Plasmonic modulators might pave the way for a new generation of compact low-power high-speed optoelectronic devices. We introduce an extremely transmitter based on plasmonic Mach-Zehnder offering capacity 4 × 36 Gbit/s footprint that is only limited by size contact pads. The array contacted through multicore fiber with channel spacing 50 μm.

We perform a simple sensitivity analysis of W1 waveguide bend in photonic crystal (PhC) where we use the information obtained to optimize PhC bend's frequency response. Within single optimization step already achieve very low power reflection coefficients over almost entire range bandgap (PBG), i.e., an achromatic bend. A further shows that there is critical rod optimized structure exhibits extraordinary high at given frequency. Hence becomes tunable from 0 % up 100 involving only small...

Reflective semiconductor optical amplifier (RSOA) fiber cavity lasers are attractive colorless, self-seeded, self-tuning, and directly modulatable sources for passive networks (PONs). They comprise of an RSOA in the network unit as active element, a distribution laser cavity, waveguide grating router, common reflective mirror with latter two positioned at remote node. In this paper, we introduce model perform simulations to elucidate recently discovered successful operation new PON source....

A method for the simulation of discontinuities in photonic crystal defect waveguides is presented. This frequency domain technique based on multiple multipole method. In contrast with other known techniques, spurious reflections (due to impedance mismatch at waveguide terminations) are avoided. The absence allows one characterize precisely intrinsic behavior sole discontinuity, reducing same time size domain. To achieve a perfect matching, guided modes infinitely long corresponding input and...

We report on the numerical structural optimization of two-dimensional photonic crystal (PhC) power dividers by using two different classes algorithms, namely, a modified truncated Newton (TN) gradient search as deterministic local scheme and an evolutionary representing probabilistic global strategies. Because severe accuracy requirements during optimization, proper PhC device has been simulated multiple-multipole program that is contained in MaX-1 software package. With both optimizer...

Eight different optimization algorithms are applied to determine the best configuration of a patch unit cell frequency selective surface used as radar absorbing material. The include seven stochastic binary optimizers, which based on concept genetic and evolutionary strategies well one quasi-deterministic optimizer an algorithm inspired by hill-climbing strategies. comparison results obtained from each shows very high probability finding global optima when special microgenetic is applied.

A finite element model was built to investigate how optimize localized plasmon resonances of an Ag-coated dielectric tip for tip-enhanced Raman spectroscopy (TERS). The relation between the resonance frequency, electric field enhancement and optical constant numerically investigated. results show that increasing refractive index can significantly red shift modes excited on tip, consequently alter enhancement. Moreover, influence width also considered. When taking all factors into account, we...

Ultra-fast, continuously tunable true-time delays are key components in many microwave and optical communications subsystems. In this paper, we introduce demonstrate a new implementation method of delay featuring settling time the order tens picoseconds. Our solution relies on splitting combining complementary phased shifted spectra (CPSS). It works for large bandwidth signals, has low complexity, offers moderate losses, can be fully integrated.

We propose a general design methodology for photonic crystal (PhC) diplexers, which is carried out along filtering T-junction. The diplexer operation investigated while carefully analyzing the dispersion relations of three different waveguide channels. All simulations are using multiple multipole method (MMP), offers perfect excitation and matching conditions all ports involved. resulting highly compact (it covers an area 13 x 9 lattice constants) simple when compared to other PhC designs.

A change of the optical coupling plasmonic particles was observed upon deformation a matrix elastomer where 50 nm gold were embedded. The mode showed higher extinction at polarization perpendicular to strain direction than parallel polarization, as induces interparticle distance change. Simulation by multiple multipole program confirmed such spectral when orientation coupled particle cluster is deformed. vector map constructed from microscopy images with different polarizations...