Active Liquid Crystal Tuning of Metallic Nanoantenna Enhanced Light Emission from Colloidal Quantum Dots

Abass, Aimi; Rodriguez, S. R. K.; Ako, Thomas; Aubert, Tangi; Verschuuren, Marc A.; Thourhout, Dries Van; Beeckman, Jeroen; Hens, Zeger; Rivas, Jaime Gómez; Maes, Björn

doi:10.1021/nl501955e

Cited by 47 publications

(46 citation statements)

References 50 publications

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“…[20][21][22] Here, we report on the forward emission from quasi-guided modes in polymer layers containing dye molecules. We describe how the emission spectrum of the system is changed by varying the thickness of the waveguide.…”

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confidence: 99%

Luminescent Metamaterials for Solid State Lighting

Nikitin

Remezani

Rivas

2015

ECS J. Solid State Sci. Technol.

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We investigate the luminescent spectrum of thin films of dye molecules embedded in a polymer layer and on top of an array of aluminum nanoparticles. The emission couples to quasi-guided modes that are efficiently coupled out to free space by scattering with the particle array. This outcoupling provides a significant enhancement of the emission in defined directions. The mode density changes and the spectrum is modified by varying the thickness of the layer. In consequence, the luminous efficacy of the layer of dye can be controlled by the layer thickness and the characteristics of the particle array. This system can be regarded as a luminescent metamaterial with designed properties that can be exploited in The invention of the efficient blue Light Emitting Diode (LED) 1 has led to the Solid State Lighting (SSL) revolution that will replace inefficient incandescent and fluorescent lamps by much more efficient light sources. Blue light is necessary for the generation of broadband white light. In a white LED this generation is usually realized through a luminescent or phosphorescent material, which is called the phosphor.2 Blue light from efficient InGaN quantum wells is absorbed by the phosphor, which emits light of a longer wavelength. White light is generated by mixing the emission of the phosphor with the fraction of non-absorbed blue light. Research on light generation in white LEDs has mainly focused on the improvement of the quantum efficiency of the phosphor by modifying the material composition and on the change of the emission spectrum in order to optimally match it to the photopic sensitivity curve of the eye. 3In this article we demonstrate a radically different approach to modify the emission intensity and spectrum of phosphors for SSL. This approach relies on coupling the emission to quasi-guided modes in the phosphor layers. These modes are very efficiently outcoupled to free space radiation by scattering with periodic arrays of metallic nanoparticles. Metallic nanoparticles support localized surface plasmon polaritons (LSPPs), which are the coherent oscillations of the free charges in the metal driven by the electromagnetic field. 4 LSPPs are resonant phenomena leading to the increase of the polarizability of the particle and, consequently, to the scattering efficiency. 5 In order to use resonant plasmonic nanoparticles in real applications, we need to have large arrays or ensembles of these nanostructures. Therefore, we investigate the modification of the emission from phosphor layers on top of periodic arrays of metallic nanoparticles. These and similar arrays have received recently a significant attention because of their capacity of supporting collective plasmonic resonances. These collective resonances are the result of the enhanced radiative coupling of LSPPs through scattering and diffraction by the particle array. Two different kinds of collective resonances in periodic arrays of plasmonic particles have been described in the literature. 6 The first kind arises in waveguides with the particl...

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confidence: 99%

Luminescent Metamaterials for Solid State Lighting

Nikitin

Remezani

Rivas

2015

ECS J. Solid State Sci. Technol.

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“…These applications require meticulous control of the flow of light in order to be optimal. Through the usage of surface plasmon resonances in metallic nanoantennas, the benefits of having strong directional scattering and enhanced light-matter interaction can be combined to open up a plethora of functionalities [10][11][12][13][14][15][16]. One of the first strategies to achieve directional scattering from plasmonic nanoantennas has been the extrapolation of established designs from radiofrequency antennas to the visible.…”

Section: Introductionmentioning

confidence: 99%

Insights into directional scattering: from coupled dipoles to asymmetric dimer nanoantennas

Abass¹,

Gutsche²,

Maes³

et al. 2016

Opt. Express

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Strong and directionally specific forward scattering from optical nanoantennas is of utmost importance for various applications in the broader context of photovoltaics and integrated light sources. Here, we outline a simple yet powerful design principle to perceive a nanoantenna that provides directional scattering into a higher index substrate based on the interference of multiple electric dipoles. A structural implementation of the electric dipole distribution is possible using plasmonic nanoparticles with a fairly simple geometry, i.e. two coupled rectangular nanoparticles, forming a dimer, on top of a substrate. The key to achieve directionality is to choose a sufficiently large size for the nanoparticles. This promotes the excitation of vertical electric dipole moments due to the bi-anisotropy of the nanoantenna. In turn, asymmetric scattering is obtained by ensuring the appropriate phase relation between the vertical electric dipole moments. The scattering strength and angular spread for an optimized nanoantenna can be shown to be broadband and robust against changes in the incidence angle. The scattering directionality is maintained even for an array configuration of the dimer. It only requires the preferred scattering direction of the isolated nanoantenna not to be prohibited by interference.

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“…These arrays are being intensively investigated because of the narrow resonances and large field enhancements that they exhibit, 18,19 which lead to a significant enhancement of the emission and a directional outcoupling of this emission in defined directions. [20][21][22][23][24][25] This is a characteristic of antenna phased arrays, which beam electromagnetic radiation due to the far-field interference of the emission by the individual antennas. From the measurements, we find that although the IQY of the dye may not be significantly modified by the antenna array, the EQY has a large dependence on the angle at which the sample is excited.…”

Section: Introductionmentioning

confidence: 99%

Control of the external photoluminescent quantum yield of emitters coupled to nanoantenna phased arrays

Lozano

Verschuuren

et al. 2015

Journal of Applied Physics

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Optical losses in metals represent the largest limitation to the external quantum yield of emitters coupled to plasmonic antennas. These losses can be at the emission wavelength, but they can be more important at shorter wavelengths, i.e., at the excitation wavelength of the emitters, where the conductivity of metals is usually lower. We present accurate measurements of the absolute external photoluminescent quantum yield of a thin layer of emitting material deposited over a periodic nanoantenna phased array. Emission and absorptance measurements of the sample are performed using a custom-made setup including an integrating sphere and variable angle excitation. The measurements reveal a strong dependence of the external quantum yield on the angle at which the optical field excites the sample. Such behavior is attributed to the coupling between far-field illumination and near-field excitation mediated by the collective resonances supported by the array. Numerical simulations confirm that the inherent losses associated with the metal can be greatly reduced by selecting an optimum angle of illumination, which boosts the light conversion efficiency in the emitting layer. This combined experimental and numerical characterization of the emission from plasmonic arrays reveals the need to carefully design the illumination to achieve the maximum external quantum yield.

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Active Liquid Crystal Tuning of Metallic Nanoantenna Enhanced Light Emission from Colloidal Quantum Dots

Cited by 47 publications

References 50 publications

Luminescent Metamaterials for Solid State Lighting

Luminescent Metamaterials for Solid State Lighting

Insights into directional scattering: from coupled dipoles to asymmetric dimer nanoantennas

Control of the external photoluminescent quantum yield of emitters coupled to nanoantenna phased arrays

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