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Oscillatory penetration of near-fields in plasmonic excitation at metal-dielectric interfaces.

Lee SC, Kang JH, Park QH, Krishna S, Brueck SR - Sci Rep (2016)

Bottom Line: This unusual field penetration is explained by the interference between these contributions, and is experimentally confirmed through an aperture which is engineered with four arms stretched out from a simple circle to manipulate a specific plasmonic excitation available in the metal film.A numerical simulation quantitatively supports the experiment.This fundamental characteristic will impact plasmonics with the near-fields designed by aperture engineering for practical applications.

View Article: PubMed Central - PubMed

Affiliation: Center for High Technology Materials and Department of Electrical and Computer Engineering, University of New Mexico, Albuquerque, NM 87106, USA.

ABSTRACT
The electric field immediately below an illuminated metal-film that is perforated with a hole array on a dielectric consists of direct transmission and scattering of the incident light through the holes and evanescent near-field from plasmonic excitations. Depending on the size and shape of the hole apertures, it exhibits an oscillatory decay in the propagation direction. This unusual field penetration is explained by the interference between these contributions, and is experimentally confirmed through an aperture which is engineered with four arms stretched out from a simple circle to manipulate a specific plasmonic excitation available in the metal film. A numerical simulation quantitatively supports the experiment. This fundamental characteristic will impact plasmonics with the near-fields designed by aperture engineering for practical applications.

No MeSH data available.


Related in: MedlinePlus

Simulation of NFI with circular aperture MPCs.(a) A plot of absorption vs wavelength of a 100 nm-thick Au MPC with a 2D square array of circular holes on the QDIP for d = 1.55, 1.9, and 2.4 μm. (b) A plot of Ez,MPC of SR1 vs z at the center of the circular aperture of three circles obtained from the side-view field map in (d), (f) and (h). (c) A plot of normalized Ez,MPC at x = d/2 vs z in each circle obtained from the depth profile in (d), (f) and (h). The dashed line on each curve follows the segment that was used for the calculation of δ in (2). 3D maps (left) and depth profiles (right) of /Ez,MPC/ at SR1 (top) and SR2 (bottom) with circular apertures of diameters, (d), (e) d = 1.55 μm (p/2); (f), (g) d = 1.9 μm; (h), (i) d = 2.4 μm. In each figure, the top row is a xy-plan view of the unit cell (3.1 × 3.1 μm2) at the middle of the absorber (along brown dashed lines at z = −0.565 μm in side view) and the bottom row is a zx-side view (along a light-blue dashed line in each plan view). The depth profile in each figure presents the variation along the selected dashed lines at x = 0.775, 0.95, and 1.2 μm (red, green, and blue dots in each plan view), corresponding to the aperture edges of three circles (d/2). A shaded region in each plot denotes the absorber. The incident light is polarized along the x-axis and κA = 0.03 was assumed.
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f2: Simulation of NFI with circular aperture MPCs.(a) A plot of absorption vs wavelength of a 100 nm-thick Au MPC with a 2D square array of circular holes on the QDIP for d = 1.55, 1.9, and 2.4 μm. (b) A plot of Ez,MPC of SR1 vs z at the center of the circular aperture of three circles obtained from the side-view field map in (d), (f) and (h). (c) A plot of normalized Ez,MPC at x = d/2 vs z in each circle obtained from the depth profile in (d), (f) and (h). The dashed line on each curve follows the segment that was used for the calculation of δ in (2). 3D maps (left) and depth profiles (right) of /Ez,MPC/ at SR1 (top) and SR2 (bottom) with circular apertures of diameters, (d), (e) d = 1.55 μm (p/2); (f), (g) d = 1.9 μm; (h), (i) d = 2.4 μm. In each figure, the top row is a xy-plan view of the unit cell (3.1 × 3.1 μm2) at the middle of the absorber (along brown dashed lines at z = −0.565 μm in side view) and the bottom row is a zx-side view (along a light-blue dashed line in each plan view). The depth profile in each figure presents the variation along the selected dashed lines at x = 0.775, 0.95, and 1.2 μm (red, green, and blue dots in each plan view), corresponding to the aperture edges of three circles (d/2). A shaded region in each plot denotes the absorber. The incident light is polarized along the x-axis and κA = 0.03 was assumed.

Mentions: SR excitation at an MPC/dielectric interface at normal incidence vanishes in the two extreme limits of an infinitesimally small aperture or an aperture as large as the pattern unit cell. Thus, SRs have the highest evanescent fields when the aperture size is comparable to p/2. In the simulation, therefore, three MPCs with circular apertures having diameters, d = 1.55 μm (=0.5p), 1.9 μm (~0.6p), and 2.4 μm (~0.8p), are examined. For convenience, these are referred to as small, medium and large circles. The details of the FDTD method used in this work have been reported elsewhere151617. The material parameters used in the simulation are summarized in Methods. The only scaling parameter in the simulation was the imaginary part in the refractive index of the absorber, κA, which shows a good agreement with the experiment at 0.03 (see Methods for discussion of κA). Figure 2a shows the absorption spectra obtained from a calculation of 1-R-T with κA = 0.03 where R and T are the reflection and transmission of the full structure. This includes the absorption by both QD stack and the metal film. As indicated in Fig. 2a, there are two pronounced peaks for SR1 and SR2 around 10 μm and 7 μm, corresponding to λSR1 and λSR2, for each circle from (1), with an additional peak at 8.3 μm dominant at large d. This peak will be discussed later. A splitting of the SR1 peak is observed as d is increased.


Oscillatory penetration of near-fields in plasmonic excitation at metal-dielectric interfaces.

Lee SC, Kang JH, Park QH, Krishna S, Brueck SR - Sci Rep (2016)

Simulation of NFI with circular aperture MPCs.(a) A plot of absorption vs wavelength of a 100 nm-thick Au MPC with a 2D square array of circular holes on the QDIP for d = 1.55, 1.9, and 2.4 μm. (b) A plot of Ez,MPC of SR1 vs z at the center of the circular aperture of three circles obtained from the side-view field map in (d), (f) and (h). (c) A plot of normalized Ez,MPC at x = d/2 vs z in each circle obtained from the depth profile in (d), (f) and (h). The dashed line on each curve follows the segment that was used for the calculation of δ in (2). 3D maps (left) and depth profiles (right) of /Ez,MPC/ at SR1 (top) and SR2 (bottom) with circular apertures of diameters, (d), (e) d = 1.55 μm (p/2); (f), (g) d = 1.9 μm; (h), (i) d = 2.4 μm. In each figure, the top row is a xy-plan view of the unit cell (3.1 × 3.1 μm2) at the middle of the absorber (along brown dashed lines at z = −0.565 μm in side view) and the bottom row is a zx-side view (along a light-blue dashed line in each plan view). The depth profile in each figure presents the variation along the selected dashed lines at x = 0.775, 0.95, and 1.2 μm (red, green, and blue dots in each plan view), corresponding to the aperture edges of three circles (d/2). A shaded region in each plot denotes the absorber. The incident light is polarized along the x-axis and κA = 0.03 was assumed.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4835736&req=5

f2: Simulation of NFI with circular aperture MPCs.(a) A plot of absorption vs wavelength of a 100 nm-thick Au MPC with a 2D square array of circular holes on the QDIP for d = 1.55, 1.9, and 2.4 μm. (b) A plot of Ez,MPC of SR1 vs z at the center of the circular aperture of three circles obtained from the side-view field map in (d), (f) and (h). (c) A plot of normalized Ez,MPC at x = d/2 vs z in each circle obtained from the depth profile in (d), (f) and (h). The dashed line on each curve follows the segment that was used for the calculation of δ in (2). 3D maps (left) and depth profiles (right) of /Ez,MPC/ at SR1 (top) and SR2 (bottom) with circular apertures of diameters, (d), (e) d = 1.55 μm (p/2); (f), (g) d = 1.9 μm; (h), (i) d = 2.4 μm. In each figure, the top row is a xy-plan view of the unit cell (3.1 × 3.1 μm2) at the middle of the absorber (along brown dashed lines at z = −0.565 μm in side view) and the bottom row is a zx-side view (along a light-blue dashed line in each plan view). The depth profile in each figure presents the variation along the selected dashed lines at x = 0.775, 0.95, and 1.2 μm (red, green, and blue dots in each plan view), corresponding to the aperture edges of three circles (d/2). A shaded region in each plot denotes the absorber. The incident light is polarized along the x-axis and κA = 0.03 was assumed.
Mentions: SR excitation at an MPC/dielectric interface at normal incidence vanishes in the two extreme limits of an infinitesimally small aperture or an aperture as large as the pattern unit cell. Thus, SRs have the highest evanescent fields when the aperture size is comparable to p/2. In the simulation, therefore, three MPCs with circular apertures having diameters, d = 1.55 μm (=0.5p), 1.9 μm (~0.6p), and 2.4 μm (~0.8p), are examined. For convenience, these are referred to as small, medium and large circles. The details of the FDTD method used in this work have been reported elsewhere151617. The material parameters used in the simulation are summarized in Methods. The only scaling parameter in the simulation was the imaginary part in the refractive index of the absorber, κA, which shows a good agreement with the experiment at 0.03 (see Methods for discussion of κA). Figure 2a shows the absorption spectra obtained from a calculation of 1-R-T with κA = 0.03 where R and T are the reflection and transmission of the full structure. This includes the absorption by both QD stack and the metal film. As indicated in Fig. 2a, there are two pronounced peaks for SR1 and SR2 around 10 μm and 7 μm, corresponding to λSR1 and λSR2, for each circle from (1), with an additional peak at 8.3 μm dominant at large d. This peak will be discussed later. A splitting of the SR1 peak is observed as d is increased.

Bottom Line: This unusual field penetration is explained by the interference between these contributions, and is experimentally confirmed through an aperture which is engineered with four arms stretched out from a simple circle to manipulate a specific plasmonic excitation available in the metal film.A numerical simulation quantitatively supports the experiment.This fundamental characteristic will impact plasmonics with the near-fields designed by aperture engineering for practical applications.

View Article: PubMed Central - PubMed

Affiliation: Center for High Technology Materials and Department of Electrical and Computer Engineering, University of New Mexico, Albuquerque, NM 87106, USA.

ABSTRACT
The electric field immediately below an illuminated metal-film that is perforated with a hole array on a dielectric consists of direct transmission and scattering of the incident light through the holes and evanescent near-field from plasmonic excitations. Depending on the size and shape of the hole apertures, it exhibits an oscillatory decay in the propagation direction. This unusual field penetration is explained by the interference between these contributions, and is experimentally confirmed through an aperture which is engineered with four arms stretched out from a simple circle to manipulate a specific plasmonic excitation available in the metal film. A numerical simulation quantitatively supports the experiment. This fundamental characteristic will impact plasmonics with the near-fields designed by aperture engineering for practical applications.

No MeSH data available.


Related in: MedlinePlus