Vahagn Mkhitaryan | ICFO-The Institute of Photonic Sciences (original) (raw)

Papers by Vahagn Mkhitaryan

Conference on Lasers and Electro-Optics, 2022

Currently, only material models with homogeneous broadening are implemented in time domain comput... more Currently, only material models with homogeneous broadening are implemented in time domain computational photonics, while modeling inhomogeneous broadening remains a challenge. We present an efficient approach to time-domain modeling of Gauss-Lorentz absorption in linear/nonlinear materials.

Conference on Lasers and Electro-Optics, 2022

We demonstrated large scale deterministic creation of single photon emitters in annealed silicon ... more We demonstrated large scale deterministic creation of single photon emitters in annealed silicon nitride on silicon oxide pillars. The estimated single photon emitter yield is approximately 50% with a lateral accuracy of ±85nm.

2022 52nd European Microwave Conference (EuMC), Sep 27, 2022

Frontiers in Optics + Laser Science 2022 (FIO, LS), 2022

A high yield (67%) method of creating single photon emitters in annealed silicon nitride on silic... more A high yield (67%) method of creating single photon emitters in annealed silicon nitride on silicon oxide pillars is demonstrated. Furthermore, the SPE emitter placement precision is found to be between ±30nm- ±85nm.

2023 International Applied Computational Electromagnetics Society Symposium (ACES)

Advanced Physics Research

Nanophotonics

Multilayer films with continuously varying indices for each layer have attracted great deal of at... more Multilayer films with continuously varying indices for each layer have attracted great deal of attention due to their superior optical, mechanical, and thermal properties. However, difficulties in fabrication have limited their application and study in scientific literature compared to multilayer films with fixed index layers. In this work we propose a neural network based inverse design technique enabled by a differentiable analytical solver for realistic design and fabrication of single material variable-index multilayer films. This approach generates multilayer films with excellent performance under ideal conditions. We furthermore address the issue of how to translate these ideal designs into practical useful devices which will naturally suffer from growth imperfections. By integrating simulated systematic and random errors just as a deposition tool would into the optimization process, we demonstrated that the same neural network that produced the ideal device can be retrained t...

Frontiers in Optics + Laser Science 2022 (FIO, LS)

A high yield (67%) method of creating single photon emitters in annealed silicon nitride on silic... more A high yield (67%) method of creating single photon emitters in annealed silicon nitride on silicon oxide pillars is demonstrated. Furthermore, the SPE emitter placement precision is found to be between ±30nm- ±85nm.

Metamaterials, Metadevices, and Metasystems 2022, Oct 3, 2022

Conference on Lasers and Electro-Optics

Currently, only material models with homogeneous broadening are implemented in time domain comput... more Currently, only material models with homogeneous broadening are implemented in time domain computational photonics, while modeling inhomogeneous broadening remains a challenge. We present an efficient approach to time-domain modeling of Gauss-Lorentz absorption in linear/nonlinear materials.

Conference on Lasers and Electro-Optics

We demonstrated large scale deterministic creation of single photon emitters in annealed silicon ... more We demonstrated large scale deterministic creation of single photon emitters in annealed silicon nitride on silicon oxide pillars. The estimated single photon emitter yield is approximately 50% with a lateral accuracy of ±85nm.

Current advances in ultrafast electron microscopy make it possible to combine optical pumping of ... more Current advances in ultrafast electron microscopy make it possible to combine optical pumping of a nanostructure and electron beam probing with subångstrom and femtosecond spatiotemporal resolution. We present a theory predicting that this technique can reveal a rich out-of-equilibrium dynamics of plasmon excitations in graphene and graphite samples. In a disruptive departure from the traditional probing of nanoscale excitations based on the identification of spectral features in the transmitted electrons, we show that measurement of angle-resolved, energy-integrated inelastic electron scattering can trace the temporal evolution of plasmons in these structures and provide momentum-resolved mode identification, thus avoiding the need for highly-monochromatic electron beams and the use of electron spectrometers. This previously unexplored approach to study the ultrafast dynamics of optical excitations can be of interest to understand and manipulate polaritons in 2D semiconductors and ...

Photonics is a key enabling technology for many applications ranging from communications to energ... more Photonics is a key enabling technology for many applications ranging from communications to energy and medicine. Its success is largely relying on our capability to appropriately control light in optical devices. To this end, the understanding of light-matter interaction occurring in the devices is a crucial element for finding effective solutions to the challenges posed by the targeted applications. This thesis is devoted to understand light-matter interaction in periodic nanostructures and ultrathin films and create modelling and design tools for functional optical devices, some of them demonstrated experimentally. We start by investigating the needed theoretical methods for describing the interaction of light with surface periodic nanostructures. We carry out a comprehensive study of the transmission, reflection and dispersion properties of 2D periodic arrays and their stacks, including, the study of more complex structures as well, such as, defects in periodic lattices, random a...

This file contains the raw dataset used in the manuscript "Tailored Nanoscale Plasmon-Enhanc... more This file contains the raw dataset used in the manuscript "Tailored Nanoscale Plasmon-Enhanced Vibrational Electron Spectroscopy" published in L. H. G. Tizei et al Nano Letters, 2020 (doi: 10.1021/acs.nanolett.9b04659) <br> Data has been acquired using Nion Swift (https://nionswift.readthedocs.io/en/stable/). Experimental details can be found in L. H. G. Tizei et al Nano Letters, 2020 (doi: 10.1021/acs.nanolett.9b04659).<br> <br> The dataset has been analyzed using the following Python libraries: Numpy, Scipy, Hyperspy, Matplotlib EELS hyperspectral images have been aligned using the Hyperspy "align1D" method. Aligned EELS hyperspectral images are saved in files finished with "_Aligned.hspy": For the strong coupling experiments:<br> Tip 1 is on hBN<br> Tip 2 is on vacuum For each of the nanowires tips, a file with the fitted coefficients are available, as well as a plot of the data and the fitted curve. Datasets have been f...

Conference on Lasers and Electro-Optics, 2021

Cutting edge electron microscopes allow to probe the optical excitations in nanostructures with s... more Cutting edge electron microscopes allow to probe the optical excitations in nanostructures with subangstrom spatial and femtosecond temporal resolution. In this study we discuss the prospects of probing the ultrafast out-of-equilibrium dynamics of plasmonic excitations in graphene and graphite samples. We show that, the plasmon excitation dynamics in nanostructured graphene and graphite can be traced through energy integrated and momentum resolved spectra of inelastically scattered electrons in contrast to more traditional energy-resolved spectroscopy approach, where highly-monochromatized electron beams and electron spectrometers with sufficient energy resolutions are essential.

Whispering gallery mode resonators (WGMRs) trap light over many optical periods using total inter... more Whispering gallery mode resonators (WGMRs) trap light over many optical periods using total internal reflection. Thereby, they host multiple narrowband circulating modes that find applications in quantum electrodynamics, optomechanics, sensing and lasing. The spherical symmetry and low field leakage of dielectric microspheres make it difficult to probe their high-quality optical modes using far-field radiation. However, local field enhancement from metallic nanoparticles (MNPs) placed at the edge of the resonators can interface the optical far-field and the bounded cavity modes. In this work, we study the interaction between whispering gallery modes and the MNP 1 ar X iv :2 11 0. 02 11 9v 1 [ ph ys ic s. op tic s] 5 O ct 2 02 1 surface plasmons with nanometric spatial resolution by using electron-beam spectroscopies in a scanning transmission electron microscope. We show that gallery modes are induced over the spectral range of the dipolar plasmons of the nanoparticle. Additionally,...

Transparent conductors are essential in many optoelectronic devices, such as displays, smart wind... more Transparent conductors are essential in many optoelectronic devices, such as displays, smart windows, light-emitting diodes and solar cells. Here we demonstrate a transparent conductor with optical loss of B1.6%, that is, even lower than that of single-layer graphene (2.3%), and transmission higher than 98% over the visible wavelength range. This was possible by an optimized antireflection design consisting in applying Al-doped ZnO and TiO2 layers with precise thicknesses to a highly conductive Ag ultrathin film. The proposed multilayer structure also possesses a low electrical resistance (5.75O 2), a figure of merit four times larger than that of indium tin oxide, the most widely used transparent conductor today, and, contrary to it, is mechanically flexible and room temperature deposited. To assess the application potentials, transparent shielding of radiofrequency and microwave interference signals with B30 dB attenuation up to 18 GHz was achieved. DOI: 10.1038/ncomms13771 OPEN

We report on the fabrication of few-atomic-layer-thick wafer-scale crystalline silver films, alon... more We report on the fabrication of few-atomic-layer-thick wafer-scale crystalline silver films, along with the observation of plasmons in the near-to-mid infrared spectral regions upon lithographic structuring. Our measured optical spectra reveal narrow plasmons (quality factor ~ 4), further supported by a low sheet resistance comparable to bulk metal in few-atomic-layer silver films down to 7 Ag(111) monolayers. Good crystal quality and plasmon narrowness are obtained despite the addition of a thin passivating dielectric, which renders our samples resilient to ambient conditions.

Conference on Lasers and Electro-Optics, 2022

Currently, only material models with homogeneous broadening are implemented in time domain comput... more Currently, only material models with homogeneous broadening are implemented in time domain computational photonics, while modeling inhomogeneous broadening remains a challenge. We present an efficient approach to time-domain modeling of Gauss-Lorentz absorption in linear/nonlinear materials.

Conference on Lasers and Electro-Optics, 2022

We demonstrated large scale deterministic creation of single photon emitters in annealed silicon ... more We demonstrated large scale deterministic creation of single photon emitters in annealed silicon nitride on silicon oxide pillars. The estimated single photon emitter yield is approximately 50% with a lateral accuracy of ±85nm.

2022 52nd European Microwave Conference (EuMC), Sep 27, 2022

Frontiers in Optics + Laser Science 2022 (FIO, LS), 2022

A high yield (67%) method of creating single photon emitters in annealed silicon nitride on silic... more A high yield (67%) method of creating single photon emitters in annealed silicon nitride on silicon oxide pillars is demonstrated. Furthermore, the SPE emitter placement precision is found to be between ±30nm- ±85nm.

2023 International Applied Computational Electromagnetics Society Symposium (ACES)

Advanced Physics Research

Nanophotonics

Multilayer films with continuously varying indices for each layer have attracted great deal of at... more Multilayer films with continuously varying indices for each layer have attracted great deal of attention due to their superior optical, mechanical, and thermal properties. However, difficulties in fabrication have limited their application and study in scientific literature compared to multilayer films with fixed index layers. In this work we propose a neural network based inverse design technique enabled by a differentiable analytical solver for realistic design and fabrication of single material variable-index multilayer films. This approach generates multilayer films with excellent performance under ideal conditions. We furthermore address the issue of how to translate these ideal designs into practical useful devices which will naturally suffer from growth imperfections. By integrating simulated systematic and random errors just as a deposition tool would into the optimization process, we demonstrated that the same neural network that produced the ideal device can be retrained t...

Frontiers in Optics + Laser Science 2022 (FIO, LS)

A high yield (67%) method of creating single photon emitters in annealed silicon nitride on silic... more A high yield (67%) method of creating single photon emitters in annealed silicon nitride on silicon oxide pillars is demonstrated. Furthermore, the SPE emitter placement precision is found to be between ±30nm- ±85nm.

Metamaterials, Metadevices, and Metasystems 2022, Oct 3, 2022

Conference on Lasers and Electro-Optics

Currently, only material models with homogeneous broadening are implemented in time domain comput... more Currently, only material models with homogeneous broadening are implemented in time domain computational photonics, while modeling inhomogeneous broadening remains a challenge. We present an efficient approach to time-domain modeling of Gauss-Lorentz absorption in linear/nonlinear materials.

Conference on Lasers and Electro-Optics

We demonstrated large scale deterministic creation of single photon emitters in annealed silicon ... more We demonstrated large scale deterministic creation of single photon emitters in annealed silicon nitride on silicon oxide pillars. The estimated single photon emitter yield is approximately 50% with a lateral accuracy of ±85nm.

Current advances in ultrafast electron microscopy make it possible to combine optical pumping of ... more Current advances in ultrafast electron microscopy make it possible to combine optical pumping of a nanostructure and electron beam probing with subångstrom and femtosecond spatiotemporal resolution. We present a theory predicting that this technique can reveal a rich out-of-equilibrium dynamics of plasmon excitations in graphene and graphite samples. In a disruptive departure from the traditional probing of nanoscale excitations based on the identification of spectral features in the transmitted electrons, we show that measurement of angle-resolved, energy-integrated inelastic electron scattering can trace the temporal evolution of plasmons in these structures and provide momentum-resolved mode identification, thus avoiding the need for highly-monochromatic electron beams and the use of electron spectrometers. This previously unexplored approach to study the ultrafast dynamics of optical excitations can be of interest to understand and manipulate polaritons in 2D semiconductors and ...

Photonics is a key enabling technology for many applications ranging from communications to energ... more Photonics is a key enabling technology for many applications ranging from communications to energy and medicine. Its success is largely relying on our capability to appropriately control light in optical devices. To this end, the understanding of light-matter interaction occurring in the devices is a crucial element for finding effective solutions to the challenges posed by the targeted applications. This thesis is devoted to understand light-matter interaction in periodic nanostructures and ultrathin films and create modelling and design tools for functional optical devices, some of them demonstrated experimentally. We start by investigating the needed theoretical methods for describing the interaction of light with surface periodic nanostructures. We carry out a comprehensive study of the transmission, reflection and dispersion properties of 2D periodic arrays and their stacks, including, the study of more complex structures as well, such as, defects in periodic lattices, random a...

This file contains the raw dataset used in the manuscript "Tailored Nanoscale Plasmon-Enhanc... more This file contains the raw dataset used in the manuscript "Tailored Nanoscale Plasmon-Enhanced Vibrational Electron Spectroscopy" published in L. H. G. Tizei et al Nano Letters, 2020 (doi: 10.1021/acs.nanolett.9b04659) <br> Data has been acquired using Nion Swift (https://nionswift.readthedocs.io/en/stable/). Experimental details can be found in L. H. G. Tizei et al Nano Letters, 2020 (doi: 10.1021/acs.nanolett.9b04659).<br> <br> The dataset has been analyzed using the following Python libraries: Numpy, Scipy, Hyperspy, Matplotlib EELS hyperspectral images have been aligned using the Hyperspy "align1D" method. Aligned EELS hyperspectral images are saved in files finished with "_Aligned.hspy": For the strong coupling experiments:<br> Tip 1 is on hBN<br> Tip 2 is on vacuum For each of the nanowires tips, a file with the fitted coefficients are available, as well as a plot of the data and the fitted curve. Datasets have been f...

Conference on Lasers and Electro-Optics, 2021

Cutting edge electron microscopes allow to probe the optical excitations in nanostructures with s... more Cutting edge electron microscopes allow to probe the optical excitations in nanostructures with subangstrom spatial and femtosecond temporal resolution. In this study we discuss the prospects of probing the ultrafast out-of-equilibrium dynamics of plasmonic excitations in graphene and graphite samples. We show that, the plasmon excitation dynamics in nanostructured graphene and graphite can be traced through energy integrated and momentum resolved spectra of inelastically scattered electrons in contrast to more traditional energy-resolved spectroscopy approach, where highly-monochromatized electron beams and electron spectrometers with sufficient energy resolutions are essential.

Whispering gallery mode resonators (WGMRs) trap light over many optical periods using total inter... more Whispering gallery mode resonators (WGMRs) trap light over many optical periods using total internal reflection. Thereby, they host multiple narrowband circulating modes that find applications in quantum electrodynamics, optomechanics, sensing and lasing. The spherical symmetry and low field leakage of dielectric microspheres make it difficult to probe their high-quality optical modes using far-field radiation. However, local field enhancement from metallic nanoparticles (MNPs) placed at the edge of the resonators can interface the optical far-field and the bounded cavity modes. In this work, we study the interaction between whispering gallery modes and the MNP 1 ar X iv :2 11 0. 02 11 9v 1 [ ph ys ic s. op tic s] 5 O ct 2 02 1 surface plasmons with nanometric spatial resolution by using electron-beam spectroscopies in a scanning transmission electron microscope. We show that gallery modes are induced over the spectral range of the dipolar plasmons of the nanoparticle. Additionally,...

Transparent conductors are essential in many optoelectronic devices, such as displays, smart wind... more Transparent conductors are essential in many optoelectronic devices, such as displays, smart windows, light-emitting diodes and solar cells. Here we demonstrate a transparent conductor with optical loss of B1.6%, that is, even lower than that of single-layer graphene (2.3%), and transmission higher than 98% over the visible wavelength range. This was possible by an optimized antireflection design consisting in applying Al-doped ZnO and TiO2 layers with precise thicknesses to a highly conductive Ag ultrathin film. The proposed multilayer structure also possesses a low electrical resistance (5.75O 2), a figure of merit four times larger than that of indium tin oxide, the most widely used transparent conductor today, and, contrary to it, is mechanically flexible and room temperature deposited. To assess the application potentials, transparent shielding of radiofrequency and microwave interference signals with B30 dB attenuation up to 18 GHz was achieved. DOI: 10.1038/ncomms13771 OPEN

We report on the fabrication of few-atomic-layer-thick wafer-scale crystalline silver films, alon... more We report on the fabrication of few-atomic-layer-thick wafer-scale crystalline silver films, along with the observation of plasmons in the near-to-mid infrared spectral regions upon lithographic structuring. Our measured optical spectra reveal narrow plasmons (quality factor ~ 4), further supported by a low sheet resistance comparable to bulk metal in few-atomic-layer silver films down to 7 Ag(111) monolayers. Good crystal quality and plasmon narrowness are obtained despite the addition of a thin passivating dielectric, which renders our samples resilient to ambient conditions.