Paulina Segovia - Academia.edu (original) (raw)
Papers by Paulina Segovia
Surface Review and Letters, 2011
We investigate experimentally the interference in far-field radiation of two contra-propagating e... more We investigate experimentally the interference in far-field radiation of two contra-propagating evanescent fields using a conventional optical microscope. A laser beam illuminates a glass-air interface under total internal reflection condition and through the proper setup a double evanescent illumination was produced. The evanescent fields radiate from the surface into the far-field domain due to small surface scatterers. Thus, coherent interference is produced in the far-field region which is correlated with the relative positions of the evanescent illumination sources. Finally, the above-described could be considered as a device for high accuracy micro-scale measurements as well as a direct visualization method of evanescent phenomena.
Optical Materials Express, 2021
The formation of laser-induced periodic surface structures (LIPSS) on Ti thin films, their phase ... more The formation of laser-induced periodic surface structures (LIPSS) on Ti thin films, their phase and stoichiometric evolution, as a function of well below ablation threshold laser fluence, and the number of pulses, is investigated. The experiments were carried out in ambient air by using a femtosecond laser at a wavelength of 1030 nm with a pulse duration of 270 fs, operating at a repetition rate of 18.6 kHz. On the one hand, the formation of LSFL composed by an either single phase (C-Ti2O3 or r-TiO2-x) or a two-phase mixture of titanium oxide (C-Ti2O3 +r-TiO2-x) is reported. The titanium oxide phases were obtained by micro-Raman spectroscopy. The orientation of the LSFL, either parallel or perpendicular with respect to the polarization of the incident beam, correlate well with the electronic nature of the titanium oxide phases. On the other hand, the results also show the formation of HSFL, this under low cumulative fluence, with periods of 398 and 460 nm with a two-phase mixture o...
Light: Science & Applications, 2018
The optical theorem, which is a consequence of the energy conservation in scattering processes, d... more The optical theorem, which is a consequence of the energy conservation in scattering processes, directly relates the forward scattering amplitude to the extinction cross-section of the object. Originally derived for planar scalar waves, it neglects the complex structure of the focused beams and the vectorial nature of the electromagnetic field. On the other hand, radially or azimuthally polarized fields and various vortex beams, essential in modern photonic technologies, possess a prominent vectorial field structure. Here, we experimentally demonstrate a complete violation of the commonly used form of the optical theorem for radially polarized beams at both visible and microwave frequencies. We show that a plasmonic particle illuminated by such a beam exhibits strong extinction, while the scattering in the forward direction is zero. The generalized formulation of the optical theorem provides agreement with the observed results. The reported effect is vital for the understanding and design of the interaction of complex vector beams carrying longitudinal field components with subwavelength objects important in imaging, communications, nanoparticle manipulation, and detection, as well as metrology.
Laser & Photonics Reviews, 2018
Hyperbolic plasmonic metamaterials provide numerous opportunities for designing unusual linear an... more Hyperbolic plasmonic metamaterials provide numerous opportunities for designing unusual linear and nonlinear optical properties. We show that the modal overlap of fundamental and second-harmonic light in an anisotropic plasmonic metamaterial slab results in the broadband enhancement of radiated second-harmonic intensity by up to 2 orders of magnitudes for TM-and TE-polarized fundamental light compared to a smooth Au film under TM-polarised illumination. The results open up possibilities to design tuneable frequency-doubling metamaterial with the goal to overcome limitations associated with classical phase matching conditions in thick nonlinear crystals.
Light: Science & Applications, 2016
Light-matter interactions can be strongly modified by the surrounding environment. Here, we repor... more Light-matter interactions can be strongly modified by the surrounding environment. Here, we report on the first experimental observation of molecular spontaneous emission inside a highly non-local metamaterial based on a plasmonic nanorod assembly. We show that the emission process is dominated not only by the topology of its local effective medium dispersion, but also by the non-local response of the composite, so that metamaterials with different geometric parameters but the same local effective medium properties exhibit different Purcell factors. A record-high enhancement of a decay rate is observed, in agreement with the developed quantitative description of the Purcell effect in a non-local medium. An engineered material non-locality introduces an additional degree of freedom into quantum electrodynamics, enabling new applications in quantum information processing, photochemistry, imaging and sensing with macroscopic composites.
Nanophotonics VI, 2016
Hyperbolic plasmonic metamaterials provide numerous opportunities for designing unusual linear an... more Hyperbolic plasmonic metamaterials provide numerous opportunities for designing unusual linear and nonlinear optical properties. Here we report a full vectorial numerical model to study SHG in a plasmonic nanorod metamaterial slab. Our frequency-domain implementation of the hydrodynamic model of the metal permittivity for conduction electrons provided a full description of the nonlinear susceptibility in a broad spectral range. We show that the modal overlap of fundamental and second-harmonic light in the plasmonic metamaterial slab results in the frequency tuneable enhancement of radiated second-harmonic intensity by up to 2 orders of magnitudes for TM- and TE-polarized fundamental light, compared to a smooth Au film under TM-polarised illumination. A double-resonant condition with both the enhancement of fundamental field and the enhanced scattering of the second-harmonic field can be realised at multiple frequencies due to the mode structure of the metamaterial slab. The nanostructured geometry of the Au nanorod metamaterial provides a larger surface area compared to the centrosymmetric crystal lattice of gold, which is needed for exploiting the intrinsic surface nonlinearity of gold. The numerical model allows us to explain experimental investigations on the spectral behaviour and radiation diagram of the second harmonic signal. In the experiments SHG generated under femtosecond excitation with varying wavelength, polarization, and angle of incidence, was characterized in backward and forward directions. We show that the excitation of plasmonic modes in the array can remarkably enhance the nonlinear response of the system, as predicted by the model. The results open up wide ranging possibilities to design tuneable frequency-doubling metamaterial with the goal to overcome limitations associated with classical phase matching conditions in thick nonlinear crystals.
Nanotechnology, 2015
Plasmonic crystals, which consist of periodic arrangements of surface features at a metaldielectr... more Plasmonic crystals, which consist of periodic arrangements of surface features at a metaldielectric interface, allow the manipulation of optical information in the form of surface plasmon polaritons. Here we investigate the excitation and propagation of plasmonic beams in and around finite size plasmonic crystals at telecom wavelengths, highlighting the effects of the crystal boundary shape and illumination conditions. Significant differences in broad plasmonic beam generation by crystals of different shapes are demonstrated, while for narrow beams, the propagation from a crystal onto the smooth metal film is less sensitive to the crystal boundary shape. We show that by controlling the boundary shape, the size and the excitation beam parameters, directional control of propagating plasmonic modes and their behaviour such as angular beam splitting, focusing power and beam width can be efficiently achieved. This provides a promising route for robust and alignment-independent integration of plasmonic crystals with optical communication components.
Scientific reports, Jan 18, 2016
The original HTML version of this Article contained a typographical error in the volume number '6... more The original HTML version of this Article contained a typographical error in the volume number '6' which was incorrectly given as '5'. This has now been corrected.
Scientific reports, Jan 15, 2016
We explore the spectral dependence of fluorescence enhancement and the associated lifetime modifi... more We explore the spectral dependence of fluorescence enhancement and the associated lifetime modification of fluorescent molecules coupled to single metal nanoparticles. Fluorescence lifetime imaging microscopy and single-particle dark-field spectroscopy are combined to correlate the dependence of fluorescence lifetime reduction on the spectral overlap between the fluorescence emission and the localised surface plasmon (LSP) spectra of individual gold nanoparticles. A maximum lifetime reduction is observed when the fluorescence and LSP resonances coincide, with good agreement provided by numerical simulations. The explicit comparison between experiment and simulation, that we obtain, offers an insight into the spectral engineering of LSP mediated fluorescence and may lead to optimized application in sensing and biomedicine.
Optics Express, 2015
If citing, it is advised that you check and use the publisher's definitive version for pagination... more If citing, it is advised that you check and use the publisher's definitive version for pagination, volume/issue, and date of publication details. And where the final published version is provided on the Research Portal, if citing you are again advised to check the publisher's website for any subsequent corrections.
Scientific reports, 2014
Plasmonic crystals provide many passive and active optical functionalities, including enhanced se... more Plasmonic crystals provide many passive and active optical functionalities, including enhanced sensing, optical nonlinearities, light extraction from LEDs and coupling to and from subwavelength waveguides. Here we study, both experimentally and numerically, the coherent control of SPP beam excitation in finite size plasmonic crystals under focussed illumination. The correct combination of the illuminating spot size, its position relative to the plasmonic crystal, wavelength and polarisation enables the efficient shaping and directionality of SPP beam launching. We show that under strongly focussed illumination, the illuminated part of the crystal acts as an antenna, launching surface plasmon waves which are subsequently filtered by the surrounding periodic lattice. Changing the illumination conditions provides rich opportunities to engineer the SPP emission pattern. This offers an alternative technique to actively modulate and control plasmonic signals, either via micro- and nano-el...
CLEO: 2014, 2014
ABSTRACT Plasmonic nanostructures can manipulate nonlinear optical phenomena via local field enha... more ABSTRACT Plasmonic nanostructures can manipulate nonlinear optical phenomena via local field enhancement, but also can serve as strong nonlinear sources themselves. Surface second-harmonic effects in nanoparticles, surfaces, and metamaterials will be analyzed via advanced hydrodynamic model.
Physical Review B, 2015
The radiation dynamics of optical emitters can be manipulated by properly designed material struc... more The radiation dynamics of optical emitters can be manipulated by properly designed material structures providing high local density of photonic states, a phenomenon often referred to as the Purcell effect. Plasmonic nanorod metamaterials with hyperbolic dispersion of electromagnetic modes are believed to deliver a significant Purcell enhancement with both broadband and non
Using a vectorial dipolar model for multiple surface plasmon-polariton (SPP) scattering, we inves... more Using a vectorial dipolar model for multiple surface plasmon-polariton (SPP) scattering, we investigate propagation and elastic (in-plane) scattering of SPP's excited in the wavelength range of 543633 nm at random nanostructured gold surfaces. The model makes use of a composed analytic Green dyadic which takes into account near- and far-field regions, with the latter being approximated by the part describing the scattering via excitation of SPP. Simultaneous SPP excitation and in-plane propagation inside square-random arrays of nanoparticles were observed with different density of particles, demonstrating the feasibility of the suggested approach. The composed Green dyadic represents an improvement of previous SPP simulations for random nanoparticles arrays since it permits SPP scattering simulations for more realistic systems with relatively large number of close, or even in contact, nanoparticles. Our results suggest that this numerical approach is quite promising for the qua...
Physical Review B, 2015
Kotel' ikov I stitute of Radio E gi ee i g a d Ele t o i s of RAS (Ulyanovsk branch),
Surface Review and Letters, 2011
We investigate experimentally the interference in far-field radiation of two contra-propagating e... more We investigate experimentally the interference in far-field radiation of two contra-propagating evanescent fields using a conventional optical microscope. A laser beam illuminates a glass-air interface under total internal reflection condition and through the proper setup a double evanescent illumination was produced. The evanescent fields radiate from the surface into the far-field domain due to small surface scatterers. Thus, coherent interference is produced in the far-field region which is correlated with the relative positions of the evanescent illumination sources. Finally, the above-described could be considered as a device for high accuracy micro-scale measurements as well as a direct visualization method of evanescent phenomena.
Optical Materials Express, 2021
The formation of laser-induced periodic surface structures (LIPSS) on Ti thin films, their phase ... more The formation of laser-induced periodic surface structures (LIPSS) on Ti thin films, their phase and stoichiometric evolution, as a function of well below ablation threshold laser fluence, and the number of pulses, is investigated. The experiments were carried out in ambient air by using a femtosecond laser at a wavelength of 1030 nm with a pulse duration of 270 fs, operating at a repetition rate of 18.6 kHz. On the one hand, the formation of LSFL composed by an either single phase (C-Ti2O3 or r-TiO2-x) or a two-phase mixture of titanium oxide (C-Ti2O3 +r-TiO2-x) is reported. The titanium oxide phases were obtained by micro-Raman spectroscopy. The orientation of the LSFL, either parallel or perpendicular with respect to the polarization of the incident beam, correlate well with the electronic nature of the titanium oxide phases. On the other hand, the results also show the formation of HSFL, this under low cumulative fluence, with periods of 398 and 460 nm with a two-phase mixture o...
Light: Science & Applications, 2018
The optical theorem, which is a consequence of the energy conservation in scattering processes, d... more The optical theorem, which is a consequence of the energy conservation in scattering processes, directly relates the forward scattering amplitude to the extinction cross-section of the object. Originally derived for planar scalar waves, it neglects the complex structure of the focused beams and the vectorial nature of the electromagnetic field. On the other hand, radially or azimuthally polarized fields and various vortex beams, essential in modern photonic technologies, possess a prominent vectorial field structure. Here, we experimentally demonstrate a complete violation of the commonly used form of the optical theorem for radially polarized beams at both visible and microwave frequencies. We show that a plasmonic particle illuminated by such a beam exhibits strong extinction, while the scattering in the forward direction is zero. The generalized formulation of the optical theorem provides agreement with the observed results. The reported effect is vital for the understanding and design of the interaction of complex vector beams carrying longitudinal field components with subwavelength objects important in imaging, communications, nanoparticle manipulation, and detection, as well as metrology.
Laser & Photonics Reviews, 2018
Hyperbolic plasmonic metamaterials provide numerous opportunities for designing unusual linear an... more Hyperbolic plasmonic metamaterials provide numerous opportunities for designing unusual linear and nonlinear optical properties. We show that the modal overlap of fundamental and second-harmonic light in an anisotropic plasmonic metamaterial slab results in the broadband enhancement of radiated second-harmonic intensity by up to 2 orders of magnitudes for TM-and TE-polarized fundamental light compared to a smooth Au film under TM-polarised illumination. The results open up possibilities to design tuneable frequency-doubling metamaterial with the goal to overcome limitations associated with classical phase matching conditions in thick nonlinear crystals.
Light: Science & Applications, 2016
Light-matter interactions can be strongly modified by the surrounding environment. Here, we repor... more Light-matter interactions can be strongly modified by the surrounding environment. Here, we report on the first experimental observation of molecular spontaneous emission inside a highly non-local metamaterial based on a plasmonic nanorod assembly. We show that the emission process is dominated not only by the topology of its local effective medium dispersion, but also by the non-local response of the composite, so that metamaterials with different geometric parameters but the same local effective medium properties exhibit different Purcell factors. A record-high enhancement of a decay rate is observed, in agreement with the developed quantitative description of the Purcell effect in a non-local medium. An engineered material non-locality introduces an additional degree of freedom into quantum electrodynamics, enabling new applications in quantum information processing, photochemistry, imaging and sensing with macroscopic composites.
Nanophotonics VI, 2016
Hyperbolic plasmonic metamaterials provide numerous opportunities for designing unusual linear an... more Hyperbolic plasmonic metamaterials provide numerous opportunities for designing unusual linear and nonlinear optical properties. Here we report a full vectorial numerical model to study SHG in a plasmonic nanorod metamaterial slab. Our frequency-domain implementation of the hydrodynamic model of the metal permittivity for conduction electrons provided a full description of the nonlinear susceptibility in a broad spectral range. We show that the modal overlap of fundamental and second-harmonic light in the plasmonic metamaterial slab results in the frequency tuneable enhancement of radiated second-harmonic intensity by up to 2 orders of magnitudes for TM- and TE-polarized fundamental light, compared to a smooth Au film under TM-polarised illumination. A double-resonant condition with both the enhancement of fundamental field and the enhanced scattering of the second-harmonic field can be realised at multiple frequencies due to the mode structure of the metamaterial slab. The nanostructured geometry of the Au nanorod metamaterial provides a larger surface area compared to the centrosymmetric crystal lattice of gold, which is needed for exploiting the intrinsic surface nonlinearity of gold. The numerical model allows us to explain experimental investigations on the spectral behaviour and radiation diagram of the second harmonic signal. In the experiments SHG generated under femtosecond excitation with varying wavelength, polarization, and angle of incidence, was characterized in backward and forward directions. We show that the excitation of plasmonic modes in the array can remarkably enhance the nonlinear response of the system, as predicted by the model. The results open up wide ranging possibilities to design tuneable frequency-doubling metamaterial with the goal to overcome limitations associated with classical phase matching conditions in thick nonlinear crystals.
Nanotechnology, 2015
Plasmonic crystals, which consist of periodic arrangements of surface features at a metaldielectr... more Plasmonic crystals, which consist of periodic arrangements of surface features at a metaldielectric interface, allow the manipulation of optical information in the form of surface plasmon polaritons. Here we investigate the excitation and propagation of plasmonic beams in and around finite size plasmonic crystals at telecom wavelengths, highlighting the effects of the crystal boundary shape and illumination conditions. Significant differences in broad plasmonic beam generation by crystals of different shapes are demonstrated, while for narrow beams, the propagation from a crystal onto the smooth metal film is less sensitive to the crystal boundary shape. We show that by controlling the boundary shape, the size and the excitation beam parameters, directional control of propagating plasmonic modes and their behaviour such as angular beam splitting, focusing power and beam width can be efficiently achieved. This provides a promising route for robust and alignment-independent integration of plasmonic crystals with optical communication components.
Scientific reports, Jan 18, 2016
The original HTML version of this Article contained a typographical error in the volume number '6... more The original HTML version of this Article contained a typographical error in the volume number '6' which was incorrectly given as '5'. This has now been corrected.
Scientific reports, Jan 15, 2016
We explore the spectral dependence of fluorescence enhancement and the associated lifetime modifi... more We explore the spectral dependence of fluorescence enhancement and the associated lifetime modification of fluorescent molecules coupled to single metal nanoparticles. Fluorescence lifetime imaging microscopy and single-particle dark-field spectroscopy are combined to correlate the dependence of fluorescence lifetime reduction on the spectral overlap between the fluorescence emission and the localised surface plasmon (LSP) spectra of individual gold nanoparticles. A maximum lifetime reduction is observed when the fluorescence and LSP resonances coincide, with good agreement provided by numerical simulations. The explicit comparison between experiment and simulation, that we obtain, offers an insight into the spectral engineering of LSP mediated fluorescence and may lead to optimized application in sensing and biomedicine.
Optics Express, 2015
If citing, it is advised that you check and use the publisher's definitive version for pagination... more If citing, it is advised that you check and use the publisher's definitive version for pagination, volume/issue, and date of publication details. And where the final published version is provided on the Research Portal, if citing you are again advised to check the publisher's website for any subsequent corrections.
Scientific reports, 2014
Plasmonic crystals provide many passive and active optical functionalities, including enhanced se... more Plasmonic crystals provide many passive and active optical functionalities, including enhanced sensing, optical nonlinearities, light extraction from LEDs and coupling to and from subwavelength waveguides. Here we study, both experimentally and numerically, the coherent control of SPP beam excitation in finite size plasmonic crystals under focussed illumination. The correct combination of the illuminating spot size, its position relative to the plasmonic crystal, wavelength and polarisation enables the efficient shaping and directionality of SPP beam launching. We show that under strongly focussed illumination, the illuminated part of the crystal acts as an antenna, launching surface plasmon waves which are subsequently filtered by the surrounding periodic lattice. Changing the illumination conditions provides rich opportunities to engineer the SPP emission pattern. This offers an alternative technique to actively modulate and control plasmonic signals, either via micro- and nano-el...
CLEO: 2014, 2014
ABSTRACT Plasmonic nanostructures can manipulate nonlinear optical phenomena via local field enha... more ABSTRACT Plasmonic nanostructures can manipulate nonlinear optical phenomena via local field enhancement, but also can serve as strong nonlinear sources themselves. Surface second-harmonic effects in nanoparticles, surfaces, and metamaterials will be analyzed via advanced hydrodynamic model.
Physical Review B, 2015
The radiation dynamics of optical emitters can be manipulated by properly designed material struc... more The radiation dynamics of optical emitters can be manipulated by properly designed material structures providing high local density of photonic states, a phenomenon often referred to as the Purcell effect. Plasmonic nanorod metamaterials with hyperbolic dispersion of electromagnetic modes are believed to deliver a significant Purcell enhancement with both broadband and non
Using a vectorial dipolar model for multiple surface plasmon-polariton (SPP) scattering, we inves... more Using a vectorial dipolar model for multiple surface plasmon-polariton (SPP) scattering, we investigate propagation and elastic (in-plane) scattering of SPP's excited in the wavelength range of 543633 nm at random nanostructured gold surfaces. The model makes use of a composed analytic Green dyadic which takes into account near- and far-field regions, with the latter being approximated by the part describing the scattering via excitation of SPP. Simultaneous SPP excitation and in-plane propagation inside square-random arrays of nanoparticles were observed with different density of particles, demonstrating the feasibility of the suggested approach. The composed Green dyadic represents an improvement of previous SPP simulations for random nanoparticles arrays since it permits SPP scattering simulations for more realistic systems with relatively large number of close, or even in contact, nanoparticles. Our results suggest that this numerical approach is quite promising for the qua...
Physical Review B, 2015
Kotel' ikov I stitute of Radio E gi ee i g a d Ele t o i s of RAS (Ulyanovsk branch),