Nathalie Vermeulen - Profile on Academia.edu (original) (raw)
Papers by Nathalie Vermeulen
Finds and Results from the Swedish Cyprus Expedition: A Gender Perspective at the Medelhavsmuseet, 2006
Power performance of a compact, broadly tunable, continuous-wave (cw) Cr 2+ :ZnSe laser pumped by... more Power performance of a compact, broadly tunable, continuous-wave (cw) Cr 2+ :ZnSe laser pumped by a thulium fiber laser at 1800 nm was investigated. In the lasing experiments, a Cr 2+ :ZnSe sample with a small-signal differential absorption coefficient of 11 cm -1 and a fluorescence lifetime of 4.6 µs was used. An astigmatically compensated x-cavity with 15 % output coupler produced as high as 640 mW of output power at 2480 nm with 2.5 W of incident pump power. Resonator losses were investigated using three different methods, and an in-depth analysis of the results was performed. The stimulated emission cross section values determined from laser threshold data and fluorescence measurements were in good agreement with each other. Finally, broad, continuous tuning of the laser was demonstrated between 2240 and 2900 nm by using an intracavity Brewster-cut MgF 2 prism and a single set of optics.
arXiv (Cornell University), Oct 4, 2019
Nonlinear-optical refraction is typically described by means of perturbation theory near the mate... more Nonlinear-optical refraction is typically described by means of perturbation theory near the material's equilibrium state. Graphene, however, can easily move far away from its equilibrium state upon optical pumping, yielding strong nonlinear responses that cannot be modeled as mere perturbations. So far, one is still lacking the required theoretical expressions to make predictions for these complex nonlinear effects and to account for their evolution in time and space. Here, this long-standing issue is solved by the derivation of population-recipe-based expressions for graphene's nonperturbative nonlinearities. The presented framework successfully predicts and explains the various nonlinearity magnitudes and signs observed for graphene over the past decade, while also being compatible with the nonlinear pulse propagation formalism commonly used for waveguides.
APL photonics, Jun 1, 2019
3D Printed Optics and Additive Photonic Manufacturing II, 2020
Mode-field matching design, 3D fabrication and characterization of down-tapers on single-mode opt... more Mode-field matching design, 3D fabrication and characterization of down-tapers on single-mode optical fiber tips for coupling to photonic integrated circuits,"
Physical Review B, 2011
The prospect for low pump-power Raman amplification in silicon waveguides has recently been boost... more The prospect for low pump-power Raman amplification in silicon waveguides has recently been boosted by theoretical studies discussing the enhancement of nonlinear phenomena in slow-light structures. In principle, the slowing down of either the pump or the signal beam is equivalent in terms of Raman gain, but in the presence of losses, we show that they play different roles in determining the net signal gain. We also investigate the impact of the mode profile in realistic slow-light waveguides on the total gain, an effect that is usually neglected in the context of stimulated Raman scattering. By taking representative losses and mode shapes into account, we provide a realistic estimation of the achievable performance of slow-light photonic crystal waveguides.
Application of Coherent Anti-Stokes Raman Scattering (CARS) Technique to the Detection of NO
Applied Spectroscopy, 1997
A coherent anti-Stokes Raman scattering (CARS) setup has been developed to detect contamination o... more A coherent anti-Stokes Raman scattering (CARS) setup has been developed to detect contamination of atmospheric nitrogen by nitric oxide (NO). To allow spatially resolved measurements and the possibility of utilizing windows close by the test volume, we chose the folded BOXCARS setup with a CARS lens of focal length 0.5 m and a diameter of 80 mm. A frequency-doubled Nd:YAG laser (= 532 nm; EL = 50 mJ; L = 10 ns; repetition rate, 10 s−1; bandwidth, 0.05 cm−1) serves as pump for a dye laser ( Ep = 25 mJ; EL = 2 mJ; bandwidth, 0.03 cm−1), which is tunable between 585 and 615 nm. Nitric oxide CARS spectra including the first hot band have been measured with high spectral resolution in a temperature range from 300 to 800 K. The detection limit of NO is on the order of 0.25% in nitrogen under atmospheric pressure. With suppression of the nonresonant background in the application of polarization CARS, the detection limit could not be scaled down in a desirable manner. The comparison between...
Proceedings of SPIE, Apr 21, 2006
Power performance of a compact, broadly tunable, continuous-wave (cw) Cr 2+ :ZnSe laser pumped by... more Power performance of a compact, broadly tunable, continuous-wave (cw) Cr 2+ :ZnSe laser pumped by a thulium fiber laser at 1800 nm was investigated. In the lasing experiments, a Cr 2+ :ZnSe sample with a small-signal differential absorption coefficient of 11 cm -1 and a fluorescence lifetime of 4.6 µs was used. An astigmatically compensated x-cavity with 15 % output coupler produced as high as 640 mW of output power at 2480 nm with 2.5 W of incident pump power. Resonator losses were investigated using three different methods, and an in-depth analysis of the results was performed. The stimulated emission cross section values determined from laser threshold data and fluorescence measurements were in good agreement with each other. Finally, broad, continuous tuning of the laser was demonstrated between 2240 and 2900 nm by using an intracavity Brewster-cut MgF 2 prism and a single set of optics.
Physical Review B, Dec 21, 2015
Numerically solving the semiconductor Bloch equations within a phenomenological relaxation time a... more Numerically solving the semiconductor Bloch equations within a phenomenological relaxation time approximation, we extract both the linear and nonlinear optical conductivities of doped graphene and gapped graphene under excitation by a laser pulse. We discuss in detail the dependence of second harmonic generation, third harmonic generation, and the Kerr effects on the doping level, the gap, and the electric field amplitude. The numerical results for weak electric fields agree with those calculated from available analytic perturbation formulas. For strong electric fields when saturation effects are important, all the effective third order nonlinear response coefficients show a strong field dependence.
Proceedings of SPIE, Apr 18, 2016
We present the design of a photonic crystal-based multilayer structure that allows to experimenta... more We present the design of a photonic crystal-based multilayer structure that allows to experimentally demonstrate, using attenuated total reflectance experiments, the existence of the predicted transverse electric (TE) polarized excitation in graphene. We show that this mode can be excited in a single layer of graphene, even at room temperature. Furthermore, we prove that the observed mode in the reflection spectra corresponds to the TEpolarized graphene excitation and not the Bloch Surface Wave of the photonic crystal experiencing grapheneinduced loss. Finally, we point out that adding an extra layer of dielectric material on top of the structure would ensure the unambiguous identification of the TE graphene mode even in the presence of fabrication errors.
Optics Letters, Feb 27, 2018
We propose a novel semi-analytic design strategy for dielectric one-dimensional multilayer biosen... more We propose a novel semi-analytic design strategy for dielectric one-dimensional multilayer biosensors that is based on a relation between the angular sensitivity and the optical power flow of the Bloch surface wave guided by the multilayer. We show that our strategy can be used to optimize both the sensor's sensitivity and figure-of-merit without the need for extensive numerical parameter sweeps.
Journal of Physics: Photonics, 2018
We present a theoretical framework for nonlinear optics of graphene and other 2D materials in lay... more We present a theoretical framework for nonlinear optics of graphene and other 2D materials in layered structures. We derive a key equation to find the effective electric field and the sheet current density in the 2D material for given incident light beams. Our approach takes into account the effect of the surrounding environment and characterizes its contribution as a structure factor. We apply our approach to two experimental setups, and discuss the structure factors for several nonlinear optical processes including second harmonic generation, third harmonic generation, and parametric frequency conversion. Our systematic study gives a strict extraction method for the nonlinear coefficients, and provides new insights in how layered structures influence the nonlinear signal observed from 2D materials.
New Journal of Physics, 2016
Optics express, Jan 5, 2015
We present a new approach to remove monolayer graphene transferred on top of a silicon-on-insulat... more We present a new approach to remove monolayer graphene transferred on top of a silicon-on-insulator (SOI) photonic integrated chip. Femtosecond laser ablation is used for the first time to remove graphene from SOI waveguides, whereas oxygen plasma etching through a metal mask is employed to peel off graphene from the grating couplers attached to the waveguides. We show by means of Raman spectroscopy and atomic force microscopy that the removal of graphene is successful with minimal damage to the underlying SOI waveguides. Finally, we employ both removal techniques to measure the contribution of graphene to the loss of grating-coupled graphene-covered SOI waveguides using the cut-back method.
Abstract—Numerical calculations based on finite-difference time-domain (FDTD) simulations for met... more Abstract—Numerical calculations based on finite-difference time-domain (FDTD) simulations for metallic nanostructures in a broad optical spectrum require an accurate modeling of the permittivity of dispersive materials. In this paper, we present the algorithms behind B-CALM (Belgium-CAlifornia Light Machine), an open-source 3D-FDTD solver simultaneously operating on multiple Graphical Processing Units (GPUs) and efficiently utilizing multi-pole dispersion models while hiding latency in inter-GPU memory transfers. Our architecture shows a reduction in computing times for multi-pole dispersion models and an almost linear speed-up with respect to the amount of used GPUs. We benchmark B-CALM by computing the absorption efficiency of a metallic nanosphere in a broad spectral range with a six-pole Lorentz model and compare it with Mie theory and with a widely used Central Processing Unit (CPU)-based FDTD simulator. 1.
Journal of Materials Chemistry C, 2018
The use of graphene in optical and photonic applications has gained much attention in recent years.
Scientific Reports, 2017
We present a practical scheme to separate the contributions of the electric quadrupole-like and t... more We present a practical scheme to separate the contributions of the electric quadrupole-like and the magnetic dipole-like effects to the forbidden second order optical nonlinear response of graphene, and give analytic expressions for the second order optical conductivities, calculated from the independent particle approximation, with relaxation described in a phenomenological way. We predict strong second order nonlinear effects, including second harmonic generation, photon drag, and difference frequency generation. We discuss in detail the controllability of these effects by tuning the chemical potential, taking advantage of the dominant role played by interband optical transitions in the response.
Journal of Lightwave Technology, 2016
General rights Copyright and moral rights for the publications made accessible in the public port... more General rights Copyright and moral rights for the publications made accessible in the public portal are retained by the authors and/or other copyright owners and it is a condition of accessing publications that users recognise and abide by the legal requirements associated with these rights. • Users may download and print one copy of any publication from the public portal for the purpose of private study or research. • You may not further distribute the material or use it for any profit-making activity or commercial gain • You may freely distribute the URL identifying the publication in the public portal Take down policy If you believe that this document breaches copyright please contact us providing details, and we will remove access to the work immediately and investigate your claim.
![Research paper thumbnail of Erratum: Third-order nonlinearity of graphene: Effects of phenomenological relaxation and finite temperature [Phys. Rev. B91, 235320 (2015)]](https://attachments.academia-assets.com/104820741/thumbnails/1.jpg)
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SPIE Proceedings, 2016
We numerically investigate the capabilities and advantages of Raman lasers based on integrated si... more We numerically investigate the capabilities and advantages of Raman lasers based on integrated single-crystal diamond ring resonators. To this end, we first model continuous-wave (CW) Raman lasing action while taking into account the lasing directionality, the linear and nonlinear losses, and the coupling of the fields between the bus and ring sections of racetrack-shaped diamond ring resonators. We then consider the design of the ring resonators for a short-wavelength infrared (SWIR) and an ultraviolet (UV) Raman laser. Using our Raman lasing model, we determine the lasing directionality, pump threshold and lasing efficiency of the SWIR and UV devices. We find that both can yield efficient CW operation with SWIR and UV lasing slope efficiencies of 33 % and 65 %, respectively. These results showcase the potential of integrated diamond ring Raman lasers for producing wavelengths that are challenging to generate with other types of integrated lasers.
Design of large scale plasmonic nanoslit arrays for arbitrary mode conversion and demultiplexing
Optics Express, 2014
Finds and Results from the Swedish Cyprus Expedition: A Gender Perspective at the Medelhavsmuseet, 2006
Power performance of a compact, broadly tunable, continuous-wave (cw) Cr 2+ :ZnSe laser pumped by... more Power performance of a compact, broadly tunable, continuous-wave (cw) Cr 2+ :ZnSe laser pumped by a thulium fiber laser at 1800 nm was investigated. In the lasing experiments, a Cr 2+ :ZnSe sample with a small-signal differential absorption coefficient of 11 cm -1 and a fluorescence lifetime of 4.6 µs was used. An astigmatically compensated x-cavity with 15 % output coupler produced as high as 640 mW of output power at 2480 nm with 2.5 W of incident pump power. Resonator losses were investigated using three different methods, and an in-depth analysis of the results was performed. The stimulated emission cross section values determined from laser threshold data and fluorescence measurements were in good agreement with each other. Finally, broad, continuous tuning of the laser was demonstrated between 2240 and 2900 nm by using an intracavity Brewster-cut MgF 2 prism and a single set of optics.
arXiv (Cornell University), Oct 4, 2019
Nonlinear-optical refraction is typically described by means of perturbation theory near the mate... more Nonlinear-optical refraction is typically described by means of perturbation theory near the material's equilibrium state. Graphene, however, can easily move far away from its equilibrium state upon optical pumping, yielding strong nonlinear responses that cannot be modeled as mere perturbations. So far, one is still lacking the required theoretical expressions to make predictions for these complex nonlinear effects and to account for their evolution in time and space. Here, this long-standing issue is solved by the derivation of population-recipe-based expressions for graphene's nonperturbative nonlinearities. The presented framework successfully predicts and explains the various nonlinearity magnitudes and signs observed for graphene over the past decade, while also being compatible with the nonlinear pulse propagation formalism commonly used for waveguides.
APL photonics, Jun 1, 2019
3D Printed Optics and Additive Photonic Manufacturing II, 2020
Mode-field matching design, 3D fabrication and characterization of down-tapers on single-mode opt... more Mode-field matching design, 3D fabrication and characterization of down-tapers on single-mode optical fiber tips for coupling to photonic integrated circuits,"
Physical Review B, 2011
The prospect for low pump-power Raman amplification in silicon waveguides has recently been boost... more The prospect for low pump-power Raman amplification in silicon waveguides has recently been boosted by theoretical studies discussing the enhancement of nonlinear phenomena in slow-light structures. In principle, the slowing down of either the pump or the signal beam is equivalent in terms of Raman gain, but in the presence of losses, we show that they play different roles in determining the net signal gain. We also investigate the impact of the mode profile in realistic slow-light waveguides on the total gain, an effect that is usually neglected in the context of stimulated Raman scattering. By taking representative losses and mode shapes into account, we provide a realistic estimation of the achievable performance of slow-light photonic crystal waveguides.
Application of Coherent Anti-Stokes Raman Scattering (CARS) Technique to the Detection of NO
Applied Spectroscopy, 1997
A coherent anti-Stokes Raman scattering (CARS) setup has been developed to detect contamination o... more A coherent anti-Stokes Raman scattering (CARS) setup has been developed to detect contamination of atmospheric nitrogen by nitric oxide (NO). To allow spatially resolved measurements and the possibility of utilizing windows close by the test volume, we chose the folded BOXCARS setup with a CARS lens of focal length 0.5 m and a diameter of 80 mm. A frequency-doubled Nd:YAG laser (= 532 nm; EL = 50 mJ; L = 10 ns; repetition rate, 10 s−1; bandwidth, 0.05 cm−1) serves as pump for a dye laser ( Ep = 25 mJ; EL = 2 mJ; bandwidth, 0.03 cm−1), which is tunable between 585 and 615 nm. Nitric oxide CARS spectra including the first hot band have been measured with high spectral resolution in a temperature range from 300 to 800 K. The detection limit of NO is on the order of 0.25% in nitrogen under atmospheric pressure. With suppression of the nonresonant background in the application of polarization CARS, the detection limit could not be scaled down in a desirable manner. The comparison between...
Proceedings of SPIE, Apr 21, 2006
Power performance of a compact, broadly tunable, continuous-wave (cw) Cr 2+ :ZnSe laser pumped by... more Power performance of a compact, broadly tunable, continuous-wave (cw) Cr 2+ :ZnSe laser pumped by a thulium fiber laser at 1800 nm was investigated. In the lasing experiments, a Cr 2+ :ZnSe sample with a small-signal differential absorption coefficient of 11 cm -1 and a fluorescence lifetime of 4.6 µs was used. An astigmatically compensated x-cavity with 15 % output coupler produced as high as 640 mW of output power at 2480 nm with 2.5 W of incident pump power. Resonator losses were investigated using three different methods, and an in-depth analysis of the results was performed. The stimulated emission cross section values determined from laser threshold data and fluorescence measurements were in good agreement with each other. Finally, broad, continuous tuning of the laser was demonstrated between 2240 and 2900 nm by using an intracavity Brewster-cut MgF 2 prism and a single set of optics.
Physical Review B, Dec 21, 2015
Numerically solving the semiconductor Bloch equations within a phenomenological relaxation time a... more Numerically solving the semiconductor Bloch equations within a phenomenological relaxation time approximation, we extract both the linear and nonlinear optical conductivities of doped graphene and gapped graphene under excitation by a laser pulse. We discuss in detail the dependence of second harmonic generation, third harmonic generation, and the Kerr effects on the doping level, the gap, and the electric field amplitude. The numerical results for weak electric fields agree with those calculated from available analytic perturbation formulas. For strong electric fields when saturation effects are important, all the effective third order nonlinear response coefficients show a strong field dependence.
Proceedings of SPIE, Apr 18, 2016
We present the design of a photonic crystal-based multilayer structure that allows to experimenta... more We present the design of a photonic crystal-based multilayer structure that allows to experimentally demonstrate, using attenuated total reflectance experiments, the existence of the predicted transverse electric (TE) polarized excitation in graphene. We show that this mode can be excited in a single layer of graphene, even at room temperature. Furthermore, we prove that the observed mode in the reflection spectra corresponds to the TEpolarized graphene excitation and not the Bloch Surface Wave of the photonic crystal experiencing grapheneinduced loss. Finally, we point out that adding an extra layer of dielectric material on top of the structure would ensure the unambiguous identification of the TE graphene mode even in the presence of fabrication errors.
Optics Letters, Feb 27, 2018
We propose a novel semi-analytic design strategy for dielectric one-dimensional multilayer biosen... more We propose a novel semi-analytic design strategy for dielectric one-dimensional multilayer biosensors that is based on a relation between the angular sensitivity and the optical power flow of the Bloch surface wave guided by the multilayer. We show that our strategy can be used to optimize both the sensor's sensitivity and figure-of-merit without the need for extensive numerical parameter sweeps.
Journal of Physics: Photonics, 2018
We present a theoretical framework for nonlinear optics of graphene and other 2D materials in lay... more We present a theoretical framework for nonlinear optics of graphene and other 2D materials in layered structures. We derive a key equation to find the effective electric field and the sheet current density in the 2D material for given incident light beams. Our approach takes into account the effect of the surrounding environment and characterizes its contribution as a structure factor. We apply our approach to two experimental setups, and discuss the structure factors for several nonlinear optical processes including second harmonic generation, third harmonic generation, and parametric frequency conversion. Our systematic study gives a strict extraction method for the nonlinear coefficients, and provides new insights in how layered structures influence the nonlinear signal observed from 2D materials.
New Journal of Physics, 2016
Optics express, Jan 5, 2015
We present a new approach to remove monolayer graphene transferred on top of a silicon-on-insulat... more We present a new approach to remove monolayer graphene transferred on top of a silicon-on-insulator (SOI) photonic integrated chip. Femtosecond laser ablation is used for the first time to remove graphene from SOI waveguides, whereas oxygen plasma etching through a metal mask is employed to peel off graphene from the grating couplers attached to the waveguides. We show by means of Raman spectroscopy and atomic force microscopy that the removal of graphene is successful with minimal damage to the underlying SOI waveguides. Finally, we employ both removal techniques to measure the contribution of graphene to the loss of grating-coupled graphene-covered SOI waveguides using the cut-back method.
Abstract—Numerical calculations based on finite-difference time-domain (FDTD) simulations for met... more Abstract—Numerical calculations based on finite-difference time-domain (FDTD) simulations for metallic nanostructures in a broad optical spectrum require an accurate modeling of the permittivity of dispersive materials. In this paper, we present the algorithms behind B-CALM (Belgium-CAlifornia Light Machine), an open-source 3D-FDTD solver simultaneously operating on multiple Graphical Processing Units (GPUs) and efficiently utilizing multi-pole dispersion models while hiding latency in inter-GPU memory transfers. Our architecture shows a reduction in computing times for multi-pole dispersion models and an almost linear speed-up with respect to the amount of used GPUs. We benchmark B-CALM by computing the absorption efficiency of a metallic nanosphere in a broad spectral range with a six-pole Lorentz model and compare it with Mie theory and with a widely used Central Processing Unit (CPU)-based FDTD simulator. 1.
Journal of Materials Chemistry C, 2018
The use of graphene in optical and photonic applications has gained much attention in recent years.
Scientific Reports, 2017
We present a practical scheme to separate the contributions of the electric quadrupole-like and t... more We present a practical scheme to separate the contributions of the electric quadrupole-like and the magnetic dipole-like effects to the forbidden second order optical nonlinear response of graphene, and give analytic expressions for the second order optical conductivities, calculated from the independent particle approximation, with relaxation described in a phenomenological way. We predict strong second order nonlinear effects, including second harmonic generation, photon drag, and difference frequency generation. We discuss in detail the controllability of these effects by tuning the chemical potential, taking advantage of the dominant role played by interband optical transitions in the response.
Journal of Lightwave Technology, 2016
General rights Copyright and moral rights for the publications made accessible in the public port... more General rights Copyright and moral rights for the publications made accessible in the public portal are retained by the authors and/or other copyright owners and it is a condition of accessing publications that users recognise and abide by the legal requirements associated with these rights. • Users may download and print one copy of any publication from the public portal for the purpose of private study or research. • You may not further distribute the material or use it for any profit-making activity or commercial gain • You may freely distribute the URL identifying the publication in the public portal Take down policy If you believe that this document breaches copyright please contact us providing details, and we will remove access to the work immediately and investigate your claim.
SPIE Proceedings, 2016
We numerically investigate the capabilities and advantages of Raman lasers based on integrated si... more We numerically investigate the capabilities and advantages of Raman lasers based on integrated single-crystal diamond ring resonators. To this end, we first model continuous-wave (CW) Raman lasing action while taking into account the lasing directionality, the linear and nonlinear losses, and the coupling of the fields between the bus and ring sections of racetrack-shaped diamond ring resonators. We then consider the design of the ring resonators for a short-wavelength infrared (SWIR) and an ultraviolet (UV) Raman laser. Using our Raman lasing model, we determine the lasing directionality, pump threshold and lasing efficiency of the SWIR and UV devices. We find that both can yield efficient CW operation with SWIR and UV lasing slope efficiencies of 33 % and 65 %, respectively. These results showcase the potential of integrated diamond ring Raman lasers for producing wavelengths that are challenging to generate with other types of integrated lasers.
Design of large scale plasmonic nanoslit arrays for arbitrary mode conversion and demultiplexing
Optics Express, 2014