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| 2. |
- Gouvea, Paula M. P., et al.
(författare)
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Internal specular reflection from nanoparticle layers on the end face of optical fibers
- 2011
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Ingår i: Journal of Applied Physics. - : AIP Publishing. - 0021-8979 .- 1089-7550. ; 109:10, s. 103114-
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Tidskriftsartikel (refereegranskat)abstract
- Metal nanoparticles deposited on a dielectric substrate exhibit an absorption peak due to localized surface plasmon resonance (LSPR). Changes in the refractive index of the surrounding medium cause the LSPR band to shift in wavelength. In this paper, gold nanoparticles were placed on the end face of an optical fiber spliced to a reflection setup. As expected in reflection geometries, the back-reflected signal exhibits a dip at wavelengths in the LSPR band when the fiber tip is surrounded by ambient air (n = 1). However, as the refractive index of the surrounding medium is increased, there is a gradual inversion from a dip (n = 1.0) to a peak (n = 2.0). To explain these results, a model based on absorption and interference between the specular reflections from the fiber/nanoparticle and nanoparticle/ambient interfaces is proposed, showing that our reflection configuration can be used in sensing applications.
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| 3. |
- Fokine, Michael, 1970-, et al.
(författare)
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Spectral features of specular reflection from nanoparticle films
- 2010
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Ingår i: Physica Status Solidi. C, Current topics in solid state physics. - : Wiley. - 1610-1634 .- 1610-1642. ; 8:9, s. 2673-2675
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Tidskriftsartikel (refereegranskat)abstract
- In this work we analyze the internal reflection (Fresnel reflection) from Au nanoparticles on the end face of optical fibers. We demonstrate that changes in the refractive index of the surrounding medium can be detected by shifts in the reflection spectra associated with changes in the Localized Surface Plasmon Resonance of the Au-Nanoparticles. The spectral response is simulated using a model based on the interference in multilayer structures and can be described by transfer-matrix method.
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| 4. |
- Pereira, Joao, et al.
(författare)
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Fabry-Perot Cavity Optimization for Absolute Strain Sensing Using Finite Element Analysis
- 2023
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Ingår i: SENSORS. - : MDPI. ; 23:21
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Tidskriftsartikel (refereegranskat)abstract
- The finite element method (FEM) was used to investigate the optical-mechanical behavior of a Fabry-Perot Interferometer (FPI) composed of a capillary segment spliced between two sections of standard optical fiber. The developed FEM model was validated by comparing it with theory and with previously published experimental data. The model was then used to show that the absolute strain on the host substrate is usually smaller than the strain measurement obtained with the sensor. Finally, the FEM model was used to propose a cavity geometry that can be produced with repeatability and that yields the correct absolute strain experienced by the host substrate, without requiring previous strain calibration.
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| 5. |
- Romani, E. C., et al.
(författare)
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Gold nanoparticles on the surface of soda-lime glass : morphological, linear and nonlinear optical characterization
- 2012
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Ingår i: Optics Express. - 1094-4087. ; 20:5, s. 5429-5439
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Tidskriftsartikel (refereegranskat)abstract
- Materials presenting high optical nonlinearity, such as materials containing metal nanoparticles (NPs), can be used in various applications in photonics. This motivated the research presented in this paper, where morphological, linear and nonlinear optical characteristics of gold NPs on the surface of bulk soda-lime glass substrates were investigated as a function of nanoparticle height. The NPs were obtained by annealing gold (Au) thin films previously deposited on the substrates. Pixel intensity histogram fitting on Atomic Force Microscopy (AFM) images was performed to obtain the thickness of the deposited film. Image analysis was employed to obtain the statistical distribution of the average height of the NPs. In addition, absorbance spectra of the samples before and after annealing were measured. Finally, the nonlinear refractive index (n(2))and the nonlinear absorption index (alpha 2) at 800 nm were obtained before and after annealing by using the thermally managed eclipse Z-scan (TM-EZ) technique with a Ti: Sapphire laser (150 fs pulses). Results show that both n2 and alpha 2 at this wavelength change signs after the annealing and that the samples presented a high nonlinear refractive index.
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