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Plasmonic propagations distances for interferometric surface plasmon resonance biosensing.

Lepage D, Carrier D, Jiménez A, Beauvais J, Dubowski JJ - Nanoscale Res Lett (2011)

Bottom Line: The result is an increased traceability of the SPR shifts for biosensing applications.The surface roughness and dielectric values for various deposition rates of very thin Au films are measured.We also investigate an interferometric SPR setup where, due to the power flux transfer between plasmon modes, the specific choice of grating coupler can either decrease or increase the plasmon propagation length.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Electrical and Computer Engineering, Université de Sherbrooke, Sherbrooke, QC J1K 2R1, Canada. Jan.J.Dubowski@USherbrooke.ca.

ABSTRACT
A surface plasmon resonance (SPR) scheme is proposed in which the local phase modulations of the coupled plasmons can interfere and yield phase-sensitive intensity modulations in the measured signal. The result is an increased traceability of the SPR shifts for biosensing applications. The main system limitation is the propagation distance of the coupled plasmon modes. This aspect is therefore studied for thin film microstructures operating in the visible and near-infrared spectral regions. The surface roughness of the substrate layer is examined for different dielectrics and deposition methods. The Au layer, on which the plasmonic modes are propagating and the biosensing occurs, is also examined. The surface roughness and dielectric values for various deposition rates of very thin Au films are measured. We also investigate an interferometric SPR setup where, due to the power flux transfer between plasmon modes, the specific choice of grating coupler can either decrease or increase the plasmon propagation length.

No MeSH data available.


Related in: MedlinePlus

ΛSP at kSP1 for various kG. The various peaks and dips are attributed to the different SPs mode coupling shown in Figure 7. A maximum in ΛSP is found when kG = ΔSP.
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Figure 8: ΛSP at kSP1 for various kG. The various peaks and dips are attributed to the different SPs mode coupling shown in Figure 7. A maximum in ΛSP is found when kG = ΔSP.

Mentions: In addition to the fabrication methods, specific designs of the interferometric architecture can help to increase propagation lengths. As detailed widely in literature, SP modes can be coupled on both interfaces of thin film architectures, i.e. on the surface and below the metal [8,17]. Simultaneously, coupling both SP modes, SP1 atop the thin film and SP2 under, opens a plethora of luminous flux exchange phenomena [8]. When coupling SPR through a grating, as in Figure 1, several coupling events can occur between SP1 and SP2, as a function of the chosen grating periodicity, PG. Figure 7 presents the EM-field intensity distribution, calculated 1 nm below the metal layer, as a function of the in-plane wavevector kx and the grating wavevector kG = 2π/PG. The intensity shown is only for the 0th diffraction order of the grating, i.e. simple transmission, for clarity. The lines illustrate the effects of the grating's diffraction on the 0th order intensity distribution. At the SP wavevectors kSP1 and kSP2, the peaks and drops in intensity correspond to various SPs flux exchange. Anti-parallel coupling phenomena arise when forward (+) and backward (-) propagating SPs are coupling. Thus, SP1+ can couple with SP1- at kG = 2/kSP1//n, SP2+ with SP2- at kG = 2/kSP2//n and SP1+/- with SP2-/+ at kG = (/kSP1/ + /kSP2/)/n, where n is the diffraction order. More interesting are the parallel coupling between SP1 and SP2 travelling in the same directions, which occurs when kG = ΔSP/n, with ΔSP = /kSP1/ - /kSP2/. The parallel coupling between SP1 and SP2, through the first diffraction order n = 1, is of specific interest as it increases the propagation distance of the SPs on the surface. The propagation distance of SP1 for various kG is presented in Figure 8, where an increase by a factor of 1.5 can be achieved when kG = ΔSP. The SP1 and SP2 modes can optically pump each other and thus combine in a hybrid guided mode, which have been studied in the literature [8]. The sensing response still comes from the reflected (or transmitted) incident light, which is modulated by the phase shift induced by the cavity. Therefore in Figure 1, the incoming light ray can directly inject SPs at kSP1, which in turn can couple through the grating with SP2 by kSP2 = kSP1 + ΔSP. The resulting guided SP mode is propagating on both interfaces and does so much further. This specific selection of grating can then be employed for SPR interferometry and increase its sensitivity.


Plasmonic propagations distances for interferometric surface plasmon resonance biosensing.

Lepage D, Carrier D, Jiménez A, Beauvais J, Dubowski JJ - Nanoscale Res Lett (2011)

ΛSP at kSP1 for various kG. The various peaks and dips are attributed to the different SPs mode coupling shown in Figure 7. A maximum in ΛSP is found when kG = ΔSP.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3211481&req=5

Figure 8: ΛSP at kSP1 for various kG. The various peaks and dips are attributed to the different SPs mode coupling shown in Figure 7. A maximum in ΛSP is found when kG = ΔSP.
Mentions: In addition to the fabrication methods, specific designs of the interferometric architecture can help to increase propagation lengths. As detailed widely in literature, SP modes can be coupled on both interfaces of thin film architectures, i.e. on the surface and below the metal [8,17]. Simultaneously, coupling both SP modes, SP1 atop the thin film and SP2 under, opens a plethora of luminous flux exchange phenomena [8]. When coupling SPR through a grating, as in Figure 1, several coupling events can occur between SP1 and SP2, as a function of the chosen grating periodicity, PG. Figure 7 presents the EM-field intensity distribution, calculated 1 nm below the metal layer, as a function of the in-plane wavevector kx and the grating wavevector kG = 2π/PG. The intensity shown is only for the 0th diffraction order of the grating, i.e. simple transmission, for clarity. The lines illustrate the effects of the grating's diffraction on the 0th order intensity distribution. At the SP wavevectors kSP1 and kSP2, the peaks and drops in intensity correspond to various SPs flux exchange. Anti-parallel coupling phenomena arise when forward (+) and backward (-) propagating SPs are coupling. Thus, SP1+ can couple with SP1- at kG = 2/kSP1//n, SP2+ with SP2- at kG = 2/kSP2//n and SP1+/- with SP2-/+ at kG = (/kSP1/ + /kSP2/)/n, where n is the diffraction order. More interesting are the parallel coupling between SP1 and SP2 travelling in the same directions, which occurs when kG = ΔSP/n, with ΔSP = /kSP1/ - /kSP2/. The parallel coupling between SP1 and SP2, through the first diffraction order n = 1, is of specific interest as it increases the propagation distance of the SPs on the surface. The propagation distance of SP1 for various kG is presented in Figure 8, where an increase by a factor of 1.5 can be achieved when kG = ΔSP. The SP1 and SP2 modes can optically pump each other and thus combine in a hybrid guided mode, which have been studied in the literature [8]. The sensing response still comes from the reflected (or transmitted) incident light, which is modulated by the phase shift induced by the cavity. Therefore in Figure 1, the incoming light ray can directly inject SPs at kSP1, which in turn can couple through the grating with SP2 by kSP2 = kSP1 + ΔSP. The resulting guided SP mode is propagating on both interfaces and does so much further. This specific selection of grating can then be employed for SPR interferometry and increase its sensitivity.

Bottom Line: The result is an increased traceability of the SPR shifts for biosensing applications.The surface roughness and dielectric values for various deposition rates of very thin Au films are measured.We also investigate an interferometric SPR setup where, due to the power flux transfer between plasmon modes, the specific choice of grating coupler can either decrease or increase the plasmon propagation length.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Electrical and Computer Engineering, Université de Sherbrooke, Sherbrooke, QC J1K 2R1, Canada. Jan.J.Dubowski@USherbrooke.ca.

ABSTRACT
A surface plasmon resonance (SPR) scheme is proposed in which the local phase modulations of the coupled plasmons can interfere and yield phase-sensitive intensity modulations in the measured signal. The result is an increased traceability of the SPR shifts for biosensing applications. The main system limitation is the propagation distance of the coupled plasmon modes. This aspect is therefore studied for thin film microstructures operating in the visible and near-infrared spectral regions. The surface roughness of the substrate layer is examined for different dielectrics and deposition methods. The Au layer, on which the plasmonic modes are propagating and the biosensing occurs, is also examined. The surface roughness and dielectric values for various deposition rates of very thin Au films are measured. We also investigate an interferometric SPR setup where, due to the power flux transfer between plasmon modes, the specific choice of grating coupler can either decrease or increase the plasmon propagation length.

No MeSH data available.


Related in: MedlinePlus