> Kik Group College of Optics and Photonics UCF
Zoomed in figure from article Phys. Rev. B 69, 45418 (2004)


The following is an overview of recent publications, including the full text in PDF format where possible. Please note: These articles may be downloaded for personal use only. Any other use requires prior permission of the author and the publisher.

NEW Superabsorbing, artificial metal films constructed from semiconductor nanoantennas Soo Jin Kim, Junghyun Park, Majid Esfandyarpour, Emanuele Fancesco Pecora, Pieter G. Kik, and Mark L. Brongersma, Nano Letters (2016) [pdf] [link]

In 1934 Wilhelm Woltersdorff demonstrated that the absorption of light in an ultrathin, freestanding film is fundamentally limited to 50%. He concluded that reaching this limit would require a film with a real-valued sheet resistance that is exactly equal to R=eta/2=188.5 Ohm/sq, where eta = mu0 eps0 is the impedance of free space. This condition can be closely approximated over a wide frequency range in metals that feature a large imaginary relative permittivity eps'', i.e. a real-valued conductivity sigma = eps0 eps'' omega. A thin, continuous sheet of semiconductor material does not facilitate such strong absorption as its complex-valued permittivity with both large real and imaginary components preclude effective impedance matching. In this work, we show how a semiconductor metafilm constructed from optically resonant semiconductor nanostructures can be created whose optical response mimics that of a metallic sheet. For this reason the fundamental absorption limit mentioned above can also be reached with semiconductor materials, opening up new opportunities for the design of ultrathin optoelectronic and light harvesting devices.

NEW Omnidirectional excitation of sidewall gap-plasmons in a hybrid gold-aluminum nanopore structure Chatdanai Lumdee and Pieter G. Kik, to be published in APL Photonics (2016)

The gap-plasmon resonance of a gold nanoparticle in a nanopore in an aluminum film is investigated in polarization dependent single particle microscopy and spectroscopy. Scattering and transmission measurements reveal that gap-plasmons of this structure can be excited and observed under near-normal incidence excitation and collection, in contrast to the more common particle-on-a-mirror structure. Correlation of numerical simulations with optical spectroscopy suggests that a local electric field enhancement factor in excess of 50 is achieved under normal incidence excitation, with a hot-spot located near the top surface of the structure. It is shown that the strong field enhancement from this sidewall gap-plasmon mode can be efficiently excited over a broad angular range. The presented plasmonic structure lends itself to implementation in low-cost, chemically stable, easily addressable biochemical sensor arrays providing large optical field enhancement factors.

NEW Electrospray deposition of uniform thickness Ge23Sb7S70 and As40S60 chalcogenide glass films, Spencer Novak, Pao-Tai Lin, Cheng Li, Nikolay Borodinov, Zhaohong Han, Corentin Monmeyran, Neil Patel, Qingyang Du, Chatdanai Lumdee, Pieter G. Kik, Weiwei Deng, Juejun Hu, Anuradha Agarwal, Igor Luzinov, and Kathleen Richardson, JoVE 54379R3 (2016)

Solution-based electrospray film deposition, which is compatible with continuous, roll-to-roll processing, is applied to chalcogenide glasses. Two chalcogenide compositions are demonstrated: Ge23Sb7S70 and As40S60, which have both been studied extensively for planar mid-infrared (mid-IR) microphotonic devices. In this approach, uniform thickness films are fabricated through the use of computer numerical controlled (CNC) motion. Chalcogenide glass (ChG) is written over the substrate by a single nozzle along a serpentine path. Films were subjected to a series of heat treatments between 100 ˚C and 200 ˚C under vacuum to drive off residual solvent and densify the films. Based on transmission Fourier transform infrared (FTIR) spectroscopy and surface roughness measurements, both compositions were found to be suitable for the fabrication of planar devices operating in the mid-IR region. Residual solvent removal was found to be much quicker for the As40S60 film as compared to Ge23Sb7S70. Based on the advantages of electrospray, direct printing of a gradient refractive index

NEW Electrically Tunable Coherent Optical Absorption in Graphene with Ion Gel, Vrinda Thareja, Ju-Hyung Kang, Hongtao Yuan, Kaveh M. Milaninia, Harold Y. Hwang, Yi Cui, Pieter G. Kik, and Mark L. Brongersma, Nano Lett. 15, 1570 (2015) [pdf] [link]

We demonstrate electrical control over coherent optical absorption in a graphene-based Salisbury screen consisting of a single layer of graphene placed in close proximity to a gold back reflector. The screen was designed to enhance light absorption at a target wavelength of 3.2 m by using a 600 nm-thick, nonabsorbing silica spacer layer. An ionic gel layer placed on top of the screen was used to electrically gate the charge density in the graphene layer. Spectroscopic reflectance measurements were performed in situ as a function of gate bias. The changes in the reflectance spectra were analyzed using a Fresnel based transfer matrix model in which graphene was treated as an infinitesimally thin sheet with a conductivity given by the Kubo formula. The analysis reveals that a careful choice of the ionic gel layer thickness can lead to optical absorption enhancements of up to 5.5 times for the Salisbury screen compared to a suspended sheet of graphene. In addition to these absorption enhancements, we demonstrate very large electrically induced changes in the optical absorption of graphene of ~3.3% per volt, the highest attained so far in a device that features an atomically thick active layer. This is attributable in part to the more effective gating achieved with the ion gel over the conventional dielectric back gates and partially by achieving a desirable coherent absorption effect linked to the presence of the thin ion gel that boosts the absorption by 40%.

NEW Heterogeneous plasmonic trimers for enhanced nonlinear optical absorption, Seyfollah Toroghi, Chatdanai Lumdee, and Pieter G. Kik, Appl. Phys. Lett. 106, 103102 (2015) [pdf] [link]

A dramatic enhancement of the thermally induced nonlinear optical response in compositionally heterogeneous plasmonic trimers is reported. It is demonstrated numerically that the nonlinear absorption performance of silver nanoparticle dimers under pulsed illumination can be enhanced by more than two orders of magnitude through the addition of only 0.1 vol.% of gold in the dimer gap. The nonlinear absorption performance of the resulting Ag-Au-Ag trimer exceeds the peak performance of isolated gold nanoparticles by a factor 40. This dramatic effect is enabled by cascaded plasmon resonance, resulting in extreme field concentration in the central nanoparticle of the trimer. The observed localized heat-generation, large optical response, and a predicted response time below 1 ns make these structures promising candidates for use in nonlinear optical limiting and optical switching.

Effect of surface roughness on substrate-tuned gold nanoparticle gap plasmon resonances, Chatdanai Lumdee, Binfeng Yun, and Pieter G. Kik, Nanoscale 7, 4250 (2015) [pdf] [link]

The effect of nanoscale surface roughness on the gap plasmon resonance of gold nanoparticles on thermally evaporated gold films is investigated experimentally and numerically. Single-particle scattering spectra obtained from 80 nm diameter gold particles on a gold film show significant particle-to-particle variation of the peak scattering wavelength of 28 nm. The experimental results are compared with numerical simulations of gold nanoparticles positioned on representative rough gold surfaces, modeled based on atomic force microscopy measurements. The predicted spectral variation and average resonance wavelength show good agreement with the measured data. The study shows that nanometer scale surface roughness can significantly affect the performance of gap plasmon-based devices.

Gap-Plasmon Enhanced Gold Nanoparticle Photoluminescence, Chatdanai Lumdee, Binfeng Yun, and Pieter G. Kik, ACS Photonics 1, 1224 (2014) [pdf] [link] [cover] [supporting info]

Gap-plasmon enhanced gold nanoparticle photoluminescence is studied experimentally at the single particle level. The photoluminescence spectra of gold nanoparticles on an Al2O3-coated gold film under both 532 nm and 633 nm excitation show a clear peak near the measured gap plasmon resonance wavelength. Comparing the collected emission spectrum with that from a gold reference film under 633 nm excitation, a peak photoluminescence enhancement factor of 28000 is observed. The spectral shape and absolute magnitude of the enhancement factors for both excitation wavelengths are reproduced using numerical calculations without the use of any free parameters. The photoluminescence enhancement is explained in terms of a gap-mode enhanced e-h pair generation rate and a wavelength-dependent enhancement of the emission efficiency.

Related publications:
2013: Wide-band Spectral Control of Au Nanoparticle Plasmon Resonances   pdf / link
2012: Voltage Controlled Resonance Tuning of Nanoscale Plasmonic Antennas   pdf / link
2010: Metal-film-induced tuning of silver nanoparticle plasmon resonances   pdf / link

Rendering of gap mode enhanced photoluminescence (left) and measured PL with and without a nanoparticle on a gold film (right)

Photothermal response enhancement in heterogeneous plasmon resonant nanoparticle trimers, Seyfollah Toroghi and Pieter G. Kik, Phys. Rev. B 90, 205414 (2014) [pdf] [link]  

The optical response of heterogeneous plasmonic trimer structures composed of a silver nanoparticle dimer and a central gold nanoparticle is investigated analytically and numerically. The plasmon resonance of the silver dimer is controlled through near-field coupling, resulting in plasmon resonance frequency matching of the silver dimer and gold monomer. This coupling condition makes it possible to increase the energy dissipation per unit volume in the gold particle by over two orders of magnitude compared to a single-particle system. It is predicted that pulsed illumination of a trimer consisting of two 80 nm diameter silver particles and a 10 nm diameter central gold particle can raise the gold particle temperature by 100 K using a pump fluence as low as 20 nJ/mm2 at a wavelength of 530 nm. This finding may have practical applications in photothermal therapy, fast thermal nonlinear optical modulation, and could enable new fundamental thermal studies at picosecond time scales.

Rendering of a gold-silver-gold plasmonic trimer, and energy level schemes of coupled modes in related nanoparticle systems

Catoptric electrodes: transparent metal electrodes using shaped surfaces, Pieter G. Kik, Opt. Lett. 39, 5114 (2014) [pdf] [link]  

An optical electrode design is presented that theoretically allows 100% optical transmission through an interdigitated metallic electrode at 50% metal areal coverage. This is achieved by redirection of light incident on embedded metal electrode lines to an angle beyond that required for total internal reflection. Full-field electromagnetic simulations using realistic material parameters demonstrate 84% frequency-averaged transmission for unpolarized illumination across the entire visible spectral range using a silver interdigitated electrode at 50% areal coverage. The redirection is achieved through specular reflection, making it non-resonant and arbitrarily broadband, provided the electrode width exceeds the optical wavelength. These findings could significantly improve the performance of photovoltaic devices and optical detectors that require high-conductivity top contacts.

Simulated operation electric fields on a silver catoptric electrode at a wavelength of 417nm (TE) and the broadband transmission spectrum for unpolarized light

Numerical prediction of the effect of nanoscale surface roughness on film-coupled nanoparticle plasmon resonances, C. Lumdee and P. G. Kik, Proc. SPIE 9163, 91631I (2014) [pdf] [link] Abstract

Plasmon-enhanced photothermal response in heterogeneous metallic trimers, S. Toroghi and P. G. Kik, Proc. SPIE 9163, 91631B (2014) [pdf] [link] Abstract

Wide-band Spectral Control of Au Nanoparticle Plasmon Resonances on a Thermally and Chemically Robust Sensing Platform, Chatdanai Lumdee, Binfeng Yun, and Pieter G. Kik, J. Phys. Chem. C 117, 19127 (2013) [pdf] [link]  

Gold nanoparticles on Al2O3-coated gold films are presented as a chemically and thermally robust platform for molecular sensing. Single particle spectroscopy as a function of Al2O3 coating thickness shows reproducible gold nanoparticle scattering spectra in the range from 690 nm to 610 nm as the Al2O3 thickness increases from 0 to 3.4 nm. Numerical simulation of these structures indicates that surface enhanced Raman spectroscopy enhancement factors in excess of 10^6 can be achieved. The stability of the Al2O3 coated structures under high power laser irradiation was tested, revealing stable scattering spectra upon irradiation with 100 W/mm2 at the particle resonance wavelength. The presented structure solves challenges with thermal stability, wavelength tuning range, and Raman background signal associated with previously attempted approaches.

Scattering spectrum of plasmon a resonant gold nanoparticle on an aluminum film anodized at different voltages

Cascaded plasmon resonances in multi-material nanoparticle trimers for extreme field enhancement, S. Toroghi, C. Lumdee, and P. G. Kik, Proc. SPIE 8809, 88091M (2013) [pdf] [link] Abstract

Optical Characteristics and Numerical Study of Gold Nanoparticles on Al2O3 coated Gold Film for Tunable Plasmonic Sensing Platforms, C. Lumdee, B. Yun, and P. G. Kik, Proc. SPIE 8809, 88091S (2013) [pdf] [link] Abstract

Controlled Surface Plasmon Resonance on Stable Substrates as an Optimized Sensing Platform, C. Lumdee, B. Yun, and P. G. Kik, Paper FTh3C.8, Frontiers in Optics Conference (2013) [pdf] [link] Abstract

Extreme plasmon resonant field enhancement in multi-material nanoparticle trimers, Seyfollah Toroghi, Chatdanai Lumdee, and Pieter G. Kik, Paper FTh3C.3, Frontiers in Optics Conference (2013) [pdf] [link] Abstract

Post-Fabrication Voltage Controlled Resonance Tuning of Nanoscale Plasmonic Antennas, Chatdanai Lumdee, Seyfollah Toroghi, and Pieter G. Kik, ACS Nano 6, 6301 (2012) [pdf] [link]  

Voltage controlled wavelength tuning of the localized surface plasmon resonance of gold nanoparticles on an aluminum film is demonstrated in single particle microscopy and spectroscopy measurements. Anodization of the Al film after nanoparticle deposition forms an aluminum oxide spacer layer between the gold particles and the Al film, modifying the particle-substrate interaction. Darkfield microscopy reveals ring-shaped scattering images from individual Au nanoparticles, indicative of plasmon resonances with a dipole moment normal to the substrate. Single particle scattering spectra show narrow plasmon resonances that can be tuned from ~580 nm to ~550 nm as the anodization voltage increases to 12 V. All observed experimental trends could be reproduced in numerical simulations. The presented approach could be used as a general post-fabrication resonance optimization step of plasmonic nanoantennas and devices.

Scattering spectrum of plasmon a resonant gold nanoparticle on an aluminum film anodized at different voltages

Cascaded field enhancement in plasmon resonant dimer nanoantennas compatible with two-dimensional nanofabrication methods, Seyfollah Toroghi and Pieter G. Kik, Appl. Phys. Lett. 101, 13116 (2012) [pdf] [link]  

Cascaded field enhancement is demonstrated in asymmetric plasmon resonant dimer nanoantennas consisting of shape-tuned ellipsoidal nanoparticles. The nanoparticles that make up the dimer have identical thickness, suggesting that the presented approach can be used to design cascaded dimer antennas compatible with standard two-dimensional top-down nanofabrication tools such as electron beam lithography and nano-imprint lithography. Cascaded excitation is achieved by modification of the in-plane particle aspect ratios in a way that keeps the resonance frequency of the individual particles fixed, while significantly changing their polarizability. The achievable field enhancement is evaluated as a function of the particle volume ratio and spacing.

Example of a standard cascaded nanoparticle antenna, and three shape tuned cascaded antenna structures with their field enhancement spectra

Cascaded plasmon resonant field enhancement in nanoparticle dimers in the point dipole limit, Seyfollah Toroghi and Pieter G. Kik, Appl. Phys. Lett. 100, 183105 (2012) [pdf] [link]  

Cascaded field enhancement in silver dimer nanostructures is investigated using a dipole-dipole interaction model. Field enhancement spectra are evaluated as a function of the particle size difference and inter-particle spacing. We observe three distinct regimes of cascaded field enhancement: hindered cascading, multiplicative cascading, and the ultimate cascading limit, depending on the dimer interaction strength. Multiplicative cascading at small inter-particle spacing leads to analytic expressions for the ultimate internal and external field enhancement factors. For silver dimers in a host with index 1.5 we obtain a maximum internal field enhancement of 2.9E3, a factor of 75 larger than that of an isolated silver nanoparticle.

Comparison of field enhancement in cascaded plasmon dimer using a point dipole model vs. using full numerical simulation

Cascaded plasmonic metamaterials for phase-controlled enhancement of nonlinear absorption and refraction, Seyfollah Toroghi and Pieter G. Kik, Phys. Rev. B 85, 045432 (2012) [pdf] [link]

The nonlinear optical properties of plasmon resonant metamaterials consisting of chains of metal nanoparticles are evaluated. Introducing particle size differences along the chains leads to the development of cascaded plasmon resonances exhibiting increased field enhancement and field confinement. The interplay between the different resonances on the structures induces a frequency dependent enhancement of the nonlinear refractive and absorptive response of the metamaterial, ultimately providing larger nonlinear susceptibility enhancement factors with engineered complex phase. It is shown that cascaded structures can provide a figure of merit for nonlinear absorption that is more than an order of magnitude larger than that obtained in non-cascaded structures. The presented approach could lead to new planar and integrated nonlinear optical modulation and switching media with improved performance compared to their non-cascaded counterparts.

Cascaded plasmon resonant nonlinear metamaterial

Taking cascaded plasmonic field enhancement to the ultimate limit in silver nanoparticle dimers, Seyfollah Toroghi and Pieter G. Kik, Proc. SPIE 8457, 84570D (2012) [pdf] [link]

Cascaded optical field enhancement in coupled plasmonic nanostructures has attracted significant attention because of field enhancement factors that dramatically exceed those observed in isolated nanostructures. While previous studies demonstrated the existence of cascaded enhancement, little work has been done to identify the requirements for achieving maximum field enhancement. Here, we investigate cascaded field enhancement in silver nanosphere dimers as a function of volume ratio and center-to-center separation, and show the requirements for achieving the ultimate cascading limit in nanoparticle dimers. We observe field enhancements that are a factor 75 larger than observed in isolated silver nanoparticles.

Voltage controlled nanoparticle plasmon resonance tuning through anodization, Chatdanai Lumdee and Pieter G. Kik, Proc. SPIE 8457, 84570T (2012) [pdf] [link]

Frequency control of plasmon resonances is important for optical sensing applications such as Surface Enhanced Raman Spectroscopy. Prior studies that investigated substrate-based control of noble metal nanoparticle plasmon resonances mostly relied on metal substrates with organic or oxide spacer layers that provided a fixed resonance frequency after particle deposition. Here we present a new approach enabling continuous resonance tuning through controlled substrate anodization. Localized Surface Plasmon tuning of single gold nanoparticles on an Al film is observed in single-particle microscopy and spectroscopy experiments. Au nanoparticles (diameter 60 nm) are deposited on 100 nm thick Al films on silicon. Dark field microscopy reveals Au nanoparticles with a dipole moment perpendicular to the aluminum surface. Subsequently an Al2O3 film is formed with voltage controlled thickness through anodization of the particle coated sample. Spectroscopy on the same particles before and after various anodization steps reveal a consistent blue shift as the oxide thickness is increased. The observed trends in the scattering peak position are explained as a voltage controlled interaction between the nanoparticles and the substrate. The experimental findings are found to closely match numerical simulations. The effects of particle size variation and spacer layer dielectric functions are investigated numerically. The presented approach could provide a post-fabrication frequency tuning step in a wide range of plasmonic devices, could enable the investigation of the optical response of metal nanostructures in a precisely controlled local environment, and could form the basis of chemically stable frequency optimized sensors.

Design of cascaded plasmon resonances for ultrafast nonlinear optical switching, Seyfollah Toroghi and Pieter G. Kik, SPIE 8054, 80540E-1 (2011) [pdf] [link]

The optical properties of cascaded plasmon resonant metallic nanocomposites are investigated. Plasmon resonances and their related field distributions are numerically evaluated in two-dimensional arrays of spherical silver nanoparticles embedded in a dielectric host. The field distributions in structures with identical particle sizes indicate the presence of a largely dipolar particle response, with a small multipole resonance contribution at high frequency. However, in arrays consisting of particles with dissimilar sizes, an additional coupled mode appears in which the dipole moment in adjacent particles is found to be anti-parallel. For increasing size-dissimilarity a higher electric field enhancement is observed inside the small metal nanospheres, indicative of a cascaded field enhancement effect. This effect may be used to enhance the nonlinear optical response of an effective medium composed of particles with engineered size dispersion and particle placement.

Field enhancement in cascaded plasmon resonant structures

Determination of optimum Si excess concentration in Er-doped Si-rich SiO2 for optical amplification at 1.54 um , Oleksandr Savchyn, Kevin R. Coffey, and Pieter G. Kik, Appl. Phys. Lett. 97, 201107 (2010) [pdf] [link]

The presence of indirect Er3+ excitation in Si-rich SiO2 is demonstrated for Si excess concentrations in the range 2.5 – 37 at.%. The Si excess concentration providing the highest density of sensitized Er3+ ions is demonstrated to be relatively insensitive to the presence of Si nanocrystals and is found to be ~ 14.5 at.% for samples without Si nanocrystals (annealed at 600C) and ~ 11.5 at.% for samples with Si nanocrystals (annealed at 1100C). The observed optimum is attributed to an increase in the density of Si-related sensitizers as the Si concentration is increased, with subsequent deactivation and removal of these sensitizers at high Si concentrations. The optimized Si excess concentration is predicted to generate maximum Er-related gain at 1.54 μm in devices based on Er-doped Si-rich SiO2.

Frequency dependent power efficiency of a nanostructured surface plasmon coupler, Amitabh Ghoshal and Pieter G. Kik, Phys. Stat. Sol. Rapid Research Letters 4, 280 (2010) [pdf] [link] [cover] [cover info]

Surface plasmon (SP) excitation on an extended thin metal film via a miniature nanoparticle-enhanced grating coupler is studied experimentally using leakage radiation spectroscopy. A universally applicable method for determining the efficiency of free-space SP excitation is developed, and the efficiency of the coupler is determined. Two distinct grating excitation modes are observed, as well as a particle-mediated excitation mode. The maximum observed coupling efficiency of the structure was approximately 3.5% at 615 nm and 670 nm, corresponding to the two grating modes of the structure.

Leakage radiation micrscopy and spectroscopy

Single particle spectroscopy study of metal-film-induced tuning of silver nanoparticle plasmon resonances, Min Hu, Amitabh Ghoshal, Manuel Marquez, and Pieter G. Kik, J. Phys. Chem. C 114, 7509 (2010) [pdf] [link]

We present an experimental study of the tunability of the silver nanoparticle localized plasmon resonance in close proximity to a gold film. Broadband tuning of the silver particle plasmon resonance from blue wavelengths into the near-IR region can be achieved due to strong electromagnetic coupling between the nanoparticle and the metal film. By altering the thickness of a thin silica spacer layer between the metal nanoparticle and the metal film the resonance frequency can be selected. Single particle spectroscopy of over 250 isolated silver nanoparticles revealed evidence for the excitation of both horizontal and vertical plasmon modes. Distinct resonance features observed in the scattering spectra were assigned to specific modes based on a dipole-dipole interaction model. The experimental results suggest that low-loss silver nanoparticles can be used in surface enhanced spectroscopy studies throughout the entire visible spectrum. The use of frequency tuned spherical metal nanoparticles on solid substrates could lead to thermally stable substrates for plasmon enhanced sensing applications, including surface enhanced Raman scattering and refractive index based biodetection methods.

Surface Plasmon Resonance Tuner - TOC graphic

High temperature optical properties of sensitized Er3+ in Si-rich SiO2 - implications for gain performance , Oleksandr Savchyn, Ravi M. Todi, Kevin R. Coffey, and Pieter G. Kik, Opt. Mat. 32, 1274 (2010) [pdf] [link]

The high-temperature photoluminescence of Er-doped Si-rich SiO2 with and without silicon nanocrystals is studied at sample temperatures in the range 20 – 200oC. The optical properties of Er-doped Si-rich SiO2 with and without silicon nanocrystals are shown to exhibit a similar temperature dependence. Based on the measured photoluminescence intensities and lifetimes it is predicted that an increase of the sample temperature from 20C to 200oC results in a decrease of the maximum optical gain at 1535 nm by a factor of ~ 1.8 and ~ 1.6 for samples with and without nanocrystals respectively. Implementation of this material in silicon photonics requires stable operation at typical processor case temperatures up to 80 – 90oC. It is demonstrated that increasing the temperature from room temperature to 90C leads to a predicted maximum optical gain reduction of ~ 1.26 for both materials. In addition, the predicted erbium related optical gain at significant inversion levels in samples processed at low temperature (600C) is a factor ~ 9 higher than for samples processed at high temperature (1060C). These findings demonstrate that relatively thermally stable gain performance of the Er-doped Si-rich SiO2 up to typical processor operating temperatures is possible and indicate that low-temperature-processed erbium-doped silicon-rich SiO2 is a technologically viable gain medium for use in silicon photonics.

Near-field enhancement of infrared intensities for f-f transitions in Er3+ ions close to the surface of silicon nanoparticles, Lesya Borowska, Stephan Fritzsche, Pieter G. Kik, and Artem E. Masunov, J. Mol. Model. 17, 423 (2010) [pdf] [link]

Erbium doped waveguide amplifiers can be used in optical integrated circuits to compensate for signal losses. Such amplifiers use stimulated emission from the first excited state (4I13/2) to the ground state (4I15/2) of Er3+ at 1.53 μm, the standard wavelength for optical communication. Since the intra-f transitions are parity forbidden for free Er3+ ions, the absorption and the emission cross sections are quite small for such doped amplifiers. To enhance the absorption, Si nanoclusters can be embedded in silica matrix. Here we investigate the effect of the Si nanocluster on the Er emission using ab initio theory for the first time. We combine multi-reference configuration interaction with one-electron spin-orbit Hamiltonian and relativistic effective core potentials. Our calculations show that the presence of a polarizable Be atom at 5A from the Er3+ ion in a crystalline environment can lead to an enhancement in the emission by a factor of three. The implications of this effect in designing more efficient optical gain materials are discussed.

Excitation wavelength-independent sensitized Er3+ concentration in as-deposited and low temperature annealed Si-rich SiO2 films, Oleksandr Savchyn, Ravi M. Todi, Kevin R. Coffey, Luis K. Ono, Beatriz Roldan Cuenya, and Pieter G. Kik, Appl. Phys. Lett. 95, 231109 (2009) [pdf] [link]

Erbium sensitization is observed in as-deposited Er3+ doped Si-rich SiO2, ruling out the involvement of Si nanocrystals in the Er3+ excitation in these samples. The Er3+ absorption cross section in this material is similar within a factor 3 to that of samples annealed at 600oC under 355nm and 532nm excitation. The density of excitable Er3+ ions is shown to be excitation wavelength independent, while the shape of the Er3+ excitation spectra is governed by a wavelength-dependent Er3+ absorption cross section. These findings enable the use of a broad range of wavelengths for the efficient excitation of this gain medium.

Structural control of nonlinear optical absorption and refraction in dense metal nanoparticle arrays, Dana C. Kohlgraf-Owens and Pieter G. Kik, Opt. Express 17, 15032 (2009) [pdf] [link]

The linear and nonlinear optical properties of a composite containing interacting spherical silver nanoparticles embedded in a dielectric host are studied as a function of interparticle separation using three dimensional frequency domain simulations. It is shown that for a fixed amount of metal, the effective third-order nonlinear susceptibility of the composite X(3) can be significantly enhanced with respect to the linear optical properties, due to a combination of resonant surface plasmon excitation and local field redistribution. It is shown that this geometry-dependent susceptibility enhancement can lead to an improved figure of merit for nonlinear absorption. Enhancement factors for the nonlinear susceptibility of the composite are calculated, and the complex nature of the enhancement factors is discussed.

Field enhancement in dense metal nanoparticle arrays

Observation of temperature-independent internal Er3+ relaxation efficiency in Si-rich SiO2 films, Oleksandr Savchyn, Ravi M. Todi, Kevin R. Coffey, and Pieter G. Kik, Appl. Phys. Lett. 94, 241115 (2009) [pdf] [link]

Time-dependent photoluminescence measurements of low-temperature-annealed Er-doped Si-rich SiO2 were conducted at sample temperatures 15-300K. The erbium internal relaxation efficiency from the second (4I11/2) to the first (4I13/2) excited state upon luminescence-center-mediated Er3+ excitation is investigated. Despite the observation of temperature-dependent relaxation rates, the erbium internal relaxation efficiency is found to be remarkably temperature-independent, which suggests that the internal relaxation efficiency is near-unity. Internal relaxation is shown to account for 50-55% of the 4I13/2 excitation events in the entire temperature range. These results demonstrate that high pump efficiency and stable operation of devices based on this material will be possible under varying thermal conditions.

Excitation of propagating surface plasmons by a periodic nanoparticle array: trade-off between particle-induced near-field excitation and damping,
Amitabh Ghoshal and Pieter G. Kik, Appl. Phys. Lett. 94, 251102 (2009) [pdf] [link]

The excitation of propagating surface plasmons (SPs) on a silver-SiO2 interface by an array of ellipsoidal silver nanoparticles is investigated using numerical simulations as a function of particle volume for three different nanoparticle aspect ratios. We find that while the SP amplitude depends sensitively on particle volume for each selected aspect ratio, the maximum SP amplitude obtained for the different particle shapes is remarkably similar. These observations are explained in terms of particle-mediated SP excitation, counteracted by a size dependent particle-induced damping. An analytical model is presented that quantitatively describes the observed trends in SP damping.

Experimental observation of mode-selective anticrossing in surface-plasmon-coupled metal nanoparticle arrays, Amitabh Ghoshal, Ivan Divliansky, and Pieter G. Kik, Appl. Phys. Lett. 94, 171108 (2009) [pdf] [link]

Surface plasmon excitation using resonant metal nanoparticles is studied experimentally. Geometry dependent reflection measurements reveal the existence of several optical resonances. Strong coupling of the in-plane nanoparticle plasmon resonance and propagating plasmons is evident from clear anticrossing behavior. Reflection measurements at high numerical aperture demonstrate the excitation of surface plasmons via out-of-plane particle polarization. The thus excited plasmons do not exhibit anticrossing in the considered frequency range. The results are explained in terms of the known surface plasmon dispersion relation and the anisotropic frequency dependent nanoparticle polarizability. These findings are important for applications utilizing surface-coupled nanoparticle plasmon resonances.

Multi-level sensitization of Er3+ in low-temperature-annealed silicon-rich SiO2, Oleksandr Savchyn, Ravi M. Todi, Kevin R. Coffey, and Pieter G. Kik, Appl. Phys. Lett. 93, 233120 (2008) [pdf] [link] Abstract

Linear and Nonlinear Effective Medium Properties of Metallodielectric Composites of Interacting Spheres and Isolated Spheroids, Dana C. Kohlgraf-Owens and Pieter G. Kik, in Plasmonics and Metamaterials, OSA Technical Digest, paper MThB3 (2008) [pdf] [link] Abstract

Numerical study of surface plasmon enhanced nonlinear absorption and refraction, Dana C. Kohlgraf-Owens and Pieter G. Kik, Optics Express 16, 16823 (2008) [pdf] [link] Abstract

Effect of hydrogen passivation on luminescence-center-mediated Er excitation in Si rich SiO2 with and without Si nanocrystals, Oleksandr Savchyn, Pieter G. Kik, Ravi M. Todi, and Kevin R. Coffey, Phys. Rev. B 77, 205438 (2008) [pdf] [link] Abstract

Simultaneous excitation of fast and slow surface plasmon polaritons in a high dielectric contrast system, Grady Webb-Wood and Pieter G. Kik, Appl. Phys. Lett. 92, 133101 (2008) [pdf] [link] Abstract

Theory and simulation of surface plasmon excitation using resonant metal nanoparticle arrays, Amitabh Ghoshal and Pieter G. Kik, J. Appl. Phys. 103, 113111 (2008) [pdf] [link] Abstract

Surface Plasmon Nanophotonics, Mark L. Brongersma and Pieter G. Kik (Eds.), Springer Series in Optical Sciences (2007) [chapter 1] [book website] Abstract

Surface Plasmon Nanophotonics - Cover

Luminescence center mediated excitation as the dominant erbium sensitization mechanism in Er-doped silicon-rich SiO2 films, Oleksandr Savchyn, Forrest R. Ruhge, Pieter G. Kik, Ravi M. Todi, Kevin R. Coffey, Haritha Nukala, and Helge Heinrich, Phys. Rev. B 76, 195419 (2007) [pdf] [link] Abstract

Optimization of surface plasmon excitation using resonant nanoparticle arrays above a silver film, Amitabh Ghoshal and Pieter G. Kik, Proc. SPIE 6641, 664119 (2007) [pdf] [link] Abstract

Demonstration of three dimensional imaging of blood vessel using a no moving parts electronic lens-based optical confocal microscope, Nabeel A. Riza, Mumtaz Sheikh, Grady Webb-Wood, and Pieter Kik, Proc. SPIE 6510, 65100J (2007) [pdf] [link] Abstract

Optical and morphological properties of MBE grown wurtzite CdxZn1-xO thin films, J.W. Mares, F.R. Ruhge, A.V. Thompson, P.G. Kik, A. Osinsky, B. Hertog, A.M. Dabiran, P.P. Chow, and W.V. Schoenfeld, Opt. Mater. 30, 346 (2007) [pdf] [link] Abstract

In-situ experimental study of a near-field lens at visible frequencies, Grady Webb-Wood, Amitabh Ghoshal, and Pieter G. Kik, Appl. Phys. Lett. 89, 193110 (2006) [pdf] [link] Abstract

Coherent far-field excitation of surface plasmons using resonantly tuned metal nanoparticle arrays, Amitabh Ghoshal, Grady Webb-Wood, Clarisse Mazuir, and Pieter G. Kik, Proc. SPIE 5927, 592714 (2005) [pdf] [link] Abstract

Silicon optical nanocrystal memory, R.J. Walters, P.G. Kik, J.D. Casperson, H.A. Atwater, R. Lindstedt, M. Giorgi, and G. Bourianoff, Appl. Phys. Lett. 85, 2622 (2004) [pdf] Abstract

Image resolution of surface-plasmon-mediated near-field focusing with planar metal films in three dimensions using finite-linewidth dipole sources, P.G. Kik, S.A. Maier, and H.A. Atwater, Phys. Rev. B 69, 45418 (2004) [pdf] [link] Abstract

Optical pulse propagation in metal nanoparticle chain waveguides, S.A. Maier, P.G. Kik, and H.A. Atwater, Phys. Rev. B 67, 205402 (2003) [pdf] Abstract

Local detection of electromagnetic energy transport below the diffraction limit in metal nanoparticle plasmon waveguides, S.A. Maier, P.G. Kik, H.A. Atwater, S. Meltzer, E. Harel, B.E. Koel, A.A.G. Requicha, Nature Materials 2, 229-232 (2003) [pdf] Abstract

Cooperative upconversion as the gain-limiting factor in Er doped miniature Al2O3 optical waveguide amplifiers, P.G. Kik and A. Polman, J. Appl. Phys. 93, 5008 (2003) [pdf] [link] Abstract

Towards an Er-doped Si nanocrystal sensitized waveguide laser, P.G. Kik, and A.Polman, Proceedings NATO Workshop OASIS (2002) [pdf] Abstract

Metal nanoparticle arrays for near field optical lithography, P.G. Kik, S.A. Maier, and H.A. Atwater, SPIE Proceedings (2002) [pdf] Abstract

Observation of coupled plasmon-polariton modes in Au nanoparticle chain waveguides of different lengths: Estimation of waveguide loss,
S. A. Maier, P. G. Kik, and H. A. Atwater, Appl. Phys. Lett. 81, 1714 (2002) [pdf] Abstract

Observation of near-field coupling in metal nanoparticle chains using far-field polarization spectroscopy, S. A. Maier, M. L. Brongersma, P. G. Kik, and H. A. Atwater, Phys. Rev. B 65, 193408 (2002) [pdf] Abstract

Plasmon printing - a new approach to near-field lithography, P.G. Kik, S.A. Maier, and H.A. Atwater, Mat. Res. Soc. Symp. Proc. 705, Y3.6 (2002) [pdf] Abstract

Design and Performance of an Erbium-Doped Silicon Waveguide Detector Operating at 1.5 um, P. G. Kik, A. Polman, S. Libertino, and S. Coffa, J. Lightwave Technol. 20, 862 (2002) [pdf] Abstract

Gain limiting processes in Er-doped Si nanocrystal waveguides in SiO2,
P. G. Kik and A. Polman, J. Appl. Phys. 91, 534 (2002) [pdf] [link] Abstract

Plasmonics - A route to nanoscale optical devices,
S.A. Maier, M.L. Brongersma, P.G. Kik, S. Meltzer, A.A.G. Requicha, and H.A. Atwater, Adv. Mater. 13, 1501 (2001) [pdf] Abstract

Pumping planar waveguide amplifiers using a coupled waveguide system,
L.H. Slooff, P.G. Kik, A. Tip, A. Polman, J. Lightwave Technol. 19, 1740 (2001) [pdf] Abstract

Exciton-erbium energy transfer in Si nanocrystal-doped SiO2,
P.G. Kik, and A. Polman, Mat. Sc. Eng. B 81, 3 (2001) [pdf] Abstract

Energy transfer in erbium doped optical waveguides based on silicon,
P.G. Kik, Ph.D. Thesis, Utrecht University, The Netherlands (2000) [pdf]

Energy backtransfer and infrared photoresponse in erbium doped silicon p-n diodes,
N. Hamelin, P.G. Kik, and A. Polman, J. Appl. Phys. 88, 5381 (2000) [pdf] Abstract

Selective modification of the Er3+ 4I11/2 branching ratio by energy transfer to Eu3+, C. Strohhfer, P.G. Kik, and A. Polman, J. Appl. Phys. 88, 4486 (2000) [pdf] Abstract

Exciton-erbium interactions in Si nanocrystal-doped SiO2,
P.G. Kik and A. Polman, J. Appl. Phys. 88, 1992 (2000) [pdf] [link] Abstract

Strong exciton-erbium coupling in Si nanocrystal-doped SiO2,
P.G. Kik, M.L. Brongersma, A. Polman, Appl. Phys. Lett. 76, 2325 (2000) [pdf] Abstract

Size-dependent electron-hole exchange interaction in Si nanocrystals,
M.L. Brongersma, P.G. Kik, A. Polman, K.S. Min. and H.A. Atwater, Appl. Phys. Lett. 76, 351 (2000) [pdf] Abstract

Optical and electrical doping of silicon with holmium,
J.F. Suyver, P.G. Kik, T. Kimura, A. Polman, G. Franz, S. Coffa, Nucl. Instrum. Meth. B 148, 497 (1999) [pdf] Abstract

Erbium doped optical-waveguide amplifiers on silicon,
P.G. Kik, A. Polman, Mat. Res. Soc. Bull. 23, 48 (1998) [pdf] [link]  

Erbium-doped phosphate glass waveguide on silicon with 4.1 dB/cm gain at 1.535 mm, Y.C. Yan, A.J. Faber, H. de Waal, P.G. Kik, and A. Polman, Appl. Phys. Lett. 71, 2922 (1997) [pdf] Abstract

Excitation and de-excitation of Er3+ in crystalline silicon,
P.G. Kik, M.J.A. de Dood, K. Kikoin, and A. Polman, Appl. Phys. Lett. 70, 1721 (1997) [pdf] Abstract

Incorporation, excitation, and de-excitation of erbium in crystal silicon,
M.J.A. de Dood, P.G. Kik, J.H. Shin, and A. Polman, Mat. Res. Soc. Symp. Proc. 422, 219 (1996)

Concentration quenching in erbium implanted alkali silicate glasses, E. Snoeks, P.G. Kik, A. Polman, Opt. Mater. 5, 159 (1996) [pdf] Abstract

Ion beam synthesis of planar opto-electronic devices,
A. Polman, E. Snoeks, G.N. van den Hoven, M.L. Brongersma, R. Serna, J.H. Shin, P.G. Kik, E. Radius, Nucl. Instrum. Meth. B 106, 393 (1995) [pdf] Abstract