Anton Kuzma

Influence of surface oxidation on plasmon resonance in monolayer of gold and silver nanoparticles

Surface plasmon resonance of gold and silver nanoparticle (NP) layers is investigated by the experiment as well as simulations. Although the good agreement was found for gold NP film, a significant mismatch in the resonance energy for silver NP film was observed. The deviation was assigned to the presence of silver oxide (Ag2O) in silver NPs. As an alternative to the NP size-dependent Drude model, the analysis based on effective medium approximation for refractive index of Ag-Ag2O material system is carried out and compared with the core-shell model. Both Mies model and numerical simulation results illustrate shift of the surface plasmon resonance due to silver NP surface oxidation.Surface plasmon resonance of gold and silver nanoparticle (NP) layers is investigated by the experiment as well as simulations. Although the good agreement was found for gold NP film, a significant mismatch in the resonance energy for silver NP film was observed. The deviation was assigned to the presence of silver oxide (Ag2O) in silver NPs. As an alternative to the NP size-dependent Drude model, the analysis based on effective medium approximation for refractive index of Ag-Ag2O material system is carried out and compared with the core-shell model. Both Mies model and numerical simulation results illustrate shift of the surface plasmon resonance due to silver NP surface oxidation.

Plasmonic properties of Au-Ag nanoparticles: Distinctiveness of metal arrangements by optical study

The core-shell arrangement of binary compound plasmonic nanoparticles (NPs) is usually verified by plasmonic extinction spectra, since microscopy-based methods cannot provide analysis of many NPs. Here, we discuss possible scenarios of different metal arrangements: (i) core-shell model, (ii) bimetallic model, and (iii) mixture of pure metal NPs. The possibility of distinguishing individual cases is discussed in accordance with numerical simulations and an alternative characterization is suggested.

Design, simulation, evaluation, and technological verification of arrayed waveguide gratings

Abstract. We present the design, simulation, evaluation, and technological verification of various low-index optical demultiplexers based on arrayed waveguide gratings (AWGs). When designing such optical demultiplexers, a set of input geometrical parameters must be first calculated. They are essential to create AWG layout that will be then simulated using commercial photonics tools. However, these tools do not support or support only partially such a fundamental calculation. Therefore, a new stand-alone tool called AWG-Parameters was developed, which strongly reduces the time needed for the design. From the calculated geometrical parameters, the AWG layouts were created and simulated using three commercial photonic tools: Optiwave, (Ottawa, Ontario, Canada), Apollo Photonics, (Ancaster, Ontario, Canada), and R-Soft, (Pasadena, California). The designs were also technologically verified. The simulated/measured transmission characteristics were evaluated by our newly developed AWG-Analyzer tool. This tool provides calculations of AWG transmission parameters, which are also missing in commercial photonic tools. Additionally, the tool provides clear definitions of calculated transmission parameters together with their textual and graphical representations. Finally, the transmission characteristics and parameters achieved from different photonic tools were compared with each other and discussed in detail. The simulated results were also compared with the measurements. Very good agreement was achieved between theoretical (AWG-Parameters tool), simulated (commercial photonic tools), and fabricated AWG transmission parameters.

Surface plasmon resonance of gold and silver nanoparticle monolayers: effect of coupling and surface oxides

Material properties are described by some physical parameters such as temperature or pressure. Optical properties of materials are very important for applications where is light as electromagnetic wave dominant. Behavior of the light in interaction with materials depends on refractive indices. These indices are same for various sizes of materials, but in nanoscale dimensions, they depend on some phenomena. Herein, we present the study of the silver (Ag) nanoparticle (NP) monolayer film and its dielectric properties. The aim of the study is to explain phenomenon why it is necessary to use effective material properties for Ag NPs, where these properties are size-dependent. The plasmonic properties of NP have been investigated by the finite domain time difference (FDTD) simulation methods. Although the good agreement of plasmonic resonances was found for gold (Au) NP film, a significant mismatch in the resonance energy for Ag NP film was observed. The deviation was assigned to the presence of silver oxide (Ag2O) in Ag NPs as a surface layer. This real structure of Ag NPs can be replaced by structure with suitable effective material properties. Results depict importance of the effective material properties in Ag NP film for reason of the presence of silver oxide. The Ag NPs with surface oxide exhibits linear tendency in the deviation of the effective dielectric function, which agrees with the experimental observations.

Effect of metal arrangement on localized surface plasmon polaritons in bimetallic nanoparticles

Colloids compound of Au/Ag nanoparticles with heterogeneous arrangement of two metals were fabricated by various techniques in the past. Laser ablation was reported as a proper technique to fabricate core/shell nanoparticles by Han et al (Appl. Phys. Lett. 92, 023116/1-023116/3 (2008)) and Chen et al (Plasmonics 7, 509-513 (2012)). The detail analysis of plasmonic properties for several metal arrangements has been done using the finite-difference time-domain (FDTD) method. The nanoparticles have been modeled as (i) core/shell nanospheres, (ii) bimetallic particles consisting of two parts (Au and Ag), or (iii) colloid consisting of pure Au and Ag nanoparticles. Results of numerical simulations show that all three investigated nanoparticle metal arrangement systems exhibit shift of the plasmonic wavelength with increase of the Ag/Au volume ratio in a similar way as recorded in the experiment. It points out that it is not possible to distinguish the metal arrangements in nanoparticles by the optical methods only and the conclusions from optical properties can be misleading. Thus optical methods can certainly prove only that bimetallic nanoparticles consist of alloy or phase separated metals.

Simulation of silicon nitride based arrayed waveguide gratings applying three different photonics tools

We present simulation of 8-channel, 100-GHz silicon nitride based AWGs using three different commercial photonics tools, namely PHASAR from Optiwave Systems Inc., APSS from Apollo Photonics Inc. and RSoft from Synopsys Inc. For this purpose we created identical waveguide structures and identical AWG layouts in these tools and performed BPM simulations. For the simulations the same calculation conditions were used. These AWGs were designed for TM-polarized light with an AWG central wavelength of 850 nm. The output of simulations, the transmission characteristics, were used to calculate the transmission parameters defining optical properties of simulated AWGs. The achieved simulated results from all three photonics tools were analyzed and compared with each other.We present simulation of 8-channel, 100-GHz silicon nitride based AWGs using three different commercial photonics tools, namely PHASAR from Optiwave Systems Inc., APSS from Apollo Photonics Inc. and RSoft from Synopsys Inc. For this purpose we created identical waveguide structures and identical AWG layouts in these tools and performed BPM simulations. For the simulations the same calculation conditions were used. These AWGs were designed for TM-polarized light with an AWG central wavelength of 850 nm. The output of simulations, the transmission characteristics, were used to calculate the transmission parameters defining optical properties of simulated AWGs. The achieved simulated results from all three photonics tools were analyzed and compared with each other.

Design of low loss silicon nitride 8-channel AWG

We present design and simulation of the low loss silicon nitride based AWG applying our proprietary AWG-Parameters tool. The AWG was designed for TM-polarized light with a central wavelength of 850...

Surface photonic crystal structures for LED emission modification

Application of photonic crystal structures (PhC) can be attractive for overall and local enhancement of light from patterned areas of the light emitting diode (LED) surface. We used interference and near-field scanning optical microscope lithography for patterning of the surface of GaAs/AlGaAs based LEDs emitted at 840 nm. Also new approach with patterned polydimethylsiloxane (PDMS) membrane applied directly on the surface of red emitting LED was investigated. The overall emission properties of prepared LED with patterned structure show enhanced light extraction efficiency, what was documented from near- and far-field measurements.

Photonic crystal based add/drop filters for sensing

We report design and simulations of photonic crystal based add/drop filter. Simulations for spectral analyses of propagated light and simulations for investigation of dispersion diagram are performed by finite-difference time-domain (FDTD) simulation method and plane wave expansion (PWE) method respectively. Add/drop filter is created as a key part of sensor application. Additional element with certain refractive index in design of add/drop filter reflects sensed humidity and by shifted spectral response of add/drop filter.

Ring resonator and Mach-Zehnder interferometer based on PDMS

Polydimethylsiloxane (PDMS) material has recently become very popular in field of microfluidics, lab on a chip technology, sensing area and photonic devices fabrication due to unique elastic and optic properties. Preparation of flexible photonic devices gives the possibility of tuning the spectral characteristic. In this contribution we tried to prepare new photonic devices based on PDMS. Main advantage of the devices is the change of the dimensions caused by different external influences as mechanical stress, temperature or chemical vapors. It favors the PDMS devices for sensor application.