This document summarizes the research of Takuya Osada on cavity optomagnonics. It discusses his work in several areas including two-species atomic BEC, cavity optomagnonics, and hybrid quantum systems. Specifically, it describes his recent work investigating magnon-Brillouin scattering in a yttrium iron garnet sphere coupled to whispering gallery modes in a cavity. It finds that the orbital angular momentum of magnons and photons can result in nonreciprocal Brillouin scattering. Cavity enhancement of the scattering was also examined. In conclusion, the interplay between spin-Hall effect in whispering gallery modes and magnon orbital angular momentum allows for investigation of reciprocal and nonreciprocal
Prospects for Electron-Ion-Circuit Hybrid Quantum Systems_AltoOsadaAlto Osada
The document summarizes research on hybrid quantum systems combining trapped electrons, trapped ions, and superconducting qubits. It discusses using trapped electrons to interface between superconducting circuits and trapped ions, enabling quantum information transfer across different physical systems. Challenges include simultaneously trapping electrons and ions with opposite charges, cooling electrons given their small mass, and introducing lasers into cryogenic environments. Potential solutions involve separate trap chips, ions acting as trapping electrodes, and resistive or sympathetic cooling through nonlinear interactions between electrons and laser-cooled ions. Overcoming these challenges could allow connecting any quantum system to light using a trapped electron interface.
1) The document summarizes the synthesis and characterization of the ferroelectric material barium strontium titanate (Ba1-xSrxTiO3 or BST) through solid state and sol-gel methods.
2) Key characterization techniques discussed are X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and dielectric measurement through impedance spectroscopy.
3) Results shown include XRD patterns demonstrating phase composition and structure of BST samples with varying strontium content, as well as frequency-dependent dielectric properties such as real and imaginary permittivity and loss tangent.
Molecular dynamics simulations of ferroelectrics with feram codeTakeshi Nishimatsu
This document discusses ferroelectric materials and molecular dynamics (MD) simulations of their properties using an effective Hamiltonian approach. Key points include:
1) Feram is an MD simulation code that models perovskite ferroelectrics like BaTiO3 using a first-principles based effective Hamiltonian.
2) Simulations of bulk BaTiO3 and PbTiO3 reproduce their phase transitions and domain structures.
3) Simulations of thin-film capacitors show the effect of "dead layers" between ferroelectrics and electrodes on polarization.
4) Direct MD simulations of the electrocaloric effect in BaTiO3 predict a temperature change under applied and removed electric fields.
ICDIM 2016 Optical detrapping in persistent phosphorsPhilippe Smet
This document summarizes research on limiting factors for the storage capacity of persistent phosphors. It finds that optically stimulated detrapping during charging may be a key bottleneck. A simple model is presented to simulate trapping and detrapping simultaneously. The model reveals that optically stimulated detrapping has a large influence on charging dynamics, even at low excitation rates, which had not been considered previously. This could explain discrepancies seen between charging and decharging behaviors. Further careful study is needed to better understand effects of excitation intensity and wavelength on trap filling and emptying dynamics, which is important for applications of these materials.
Optical detrapping in persistent phosphors - talk at PRE'16Philippe Smet
We described the positive (trapping and energy storage) and negative (trap depletion) effects of exciting persistent or glow-in-the-dark phosphors, by combining experimental input and modelling. The trapping process is clearly more dynamic and non-linear than previously realised.
Talk presented at the PRE'16 conference on the photoluminescence of rare earth ions, organized by Clemson U in Greenville, South Carolina, US (June 8-10, 2016)
ESTE2016 Detrapping in persistent phosphorsPhilippe Smet
Presentation given at the 6th International Conference on Excited States of Transition Elements (ESTE 2016), August 23 2016. Presentation discusses detrapping mechanisms in persistent phosphors, focussing on optical and mechanical detrapping.
The document summarizes research on magnetism at oxide interfaces. It discusses how interfaces between complex oxide materials like LaAlO3 and SrTiO3 can exhibit emergent properties not present in the constituent materials, such as ferromagnetism. Experimental techniques like SQUID, torque magnetometry, and XMCD are used to study the magnetic behavior and determine its origin. Theoretical predictions and XAS data indicate the magnetism arises from a reconstructed dxy orbital state of interfacial Ti3+ ions enabled by symmetry breaking and electronic reconstruction at the interface. Potential device applications involving spin injection and field effect transistors are also presented.
SEM-CL presentation at ICOM 2015 - Budva MontenegroPhilippe Smet
Examples of SEM-CL in combination with EDX, for use in phosphor research. From phosphor evaluation at the microscopic scale to single particle analysis
Prospects for Electron-Ion-Circuit Hybrid Quantum Systems_AltoOsadaAlto Osada
The document summarizes research on hybrid quantum systems combining trapped electrons, trapped ions, and superconducting qubits. It discusses using trapped electrons to interface between superconducting circuits and trapped ions, enabling quantum information transfer across different physical systems. Challenges include simultaneously trapping electrons and ions with opposite charges, cooling electrons given their small mass, and introducing lasers into cryogenic environments. Potential solutions involve separate trap chips, ions acting as trapping electrodes, and resistive or sympathetic cooling through nonlinear interactions between electrons and laser-cooled ions. Overcoming these challenges could allow connecting any quantum system to light using a trapped electron interface.
1) The document summarizes the synthesis and characterization of the ferroelectric material barium strontium titanate (Ba1-xSrxTiO3 or BST) through solid state and sol-gel methods.
2) Key characterization techniques discussed are X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and dielectric measurement through impedance spectroscopy.
3) Results shown include XRD patterns demonstrating phase composition and structure of BST samples with varying strontium content, as well as frequency-dependent dielectric properties such as real and imaginary permittivity and loss tangent.
Molecular dynamics simulations of ferroelectrics with feram codeTakeshi Nishimatsu
This document discusses ferroelectric materials and molecular dynamics (MD) simulations of their properties using an effective Hamiltonian approach. Key points include:
1) Feram is an MD simulation code that models perovskite ferroelectrics like BaTiO3 using a first-principles based effective Hamiltonian.
2) Simulations of bulk BaTiO3 and PbTiO3 reproduce their phase transitions and domain structures.
3) Simulations of thin-film capacitors show the effect of "dead layers" between ferroelectrics and electrodes on polarization.
4) Direct MD simulations of the electrocaloric effect in BaTiO3 predict a temperature change under applied and removed electric fields.
ICDIM 2016 Optical detrapping in persistent phosphorsPhilippe Smet
This document summarizes research on limiting factors for the storage capacity of persistent phosphors. It finds that optically stimulated detrapping during charging may be a key bottleneck. A simple model is presented to simulate trapping and detrapping simultaneously. The model reveals that optically stimulated detrapping has a large influence on charging dynamics, even at low excitation rates, which had not been considered previously. This could explain discrepancies seen between charging and decharging behaviors. Further careful study is needed to better understand effects of excitation intensity and wavelength on trap filling and emptying dynamics, which is important for applications of these materials.
Optical detrapping in persistent phosphors - talk at PRE'16Philippe Smet
We described the positive (trapping and energy storage) and negative (trap depletion) effects of exciting persistent or glow-in-the-dark phosphors, by combining experimental input and modelling. The trapping process is clearly more dynamic and non-linear than previously realised.
Talk presented at the PRE'16 conference on the photoluminescence of rare earth ions, organized by Clemson U in Greenville, South Carolina, US (June 8-10, 2016)
ESTE2016 Detrapping in persistent phosphorsPhilippe Smet
Presentation given at the 6th International Conference on Excited States of Transition Elements (ESTE 2016), August 23 2016. Presentation discusses detrapping mechanisms in persistent phosphors, focussing on optical and mechanical detrapping.
The document summarizes research on magnetism at oxide interfaces. It discusses how interfaces between complex oxide materials like LaAlO3 and SrTiO3 can exhibit emergent properties not present in the constituent materials, such as ferromagnetism. Experimental techniques like SQUID, torque magnetometry, and XMCD are used to study the magnetic behavior and determine its origin. Theoretical predictions and XAS data indicate the magnetism arises from a reconstructed dxy orbital state of interfacial Ti3+ ions enabled by symmetry breaking and electronic reconstruction at the interface. Potential device applications involving spin injection and field effect transistors are also presented.
SEM-CL presentation at ICOM 2015 - Budva MontenegroPhilippe Smet
Examples of SEM-CL in combination with EDX, for use in phosphor research. From phosphor evaluation at the microscopic scale to single particle analysis
Role of excitonic effects in nonlinear optical properties of 2D materialsClaudio Attaccalite
The document discusses the role of excitonic effects in nonlinear optical properties of 2D materials. It presents a real-time approach to calculate nonlinear optics that includes excitonic effects using a dynamical polarization consistent with periodic boundary conditions. Calculations show excitonic effects enhance second harmonic generation at resonant energies in materials like MoS2 and h-BN. Excitonic effects also impact third harmonic generation by redistributing intensity and reducing it at resonant energies. The approach is implemented in an open source nonlinear optics module.
This group is working to develop the systems needed to trap and laser cool barium and lanthanum ions for use in quantum information experiments. They have:
1) Built a cavity to frequency double infrared laser light to 490nm blue light needed to laser cool barium ions. They achieved 74.43μW of 490nm light from 72mW of infrared input.
2) Modeled an ion trap and determined voltages that can stably trap lanthanum ions while ejecting contaminant lanthanum ions.
3) Designed an imaging system using multiple lenses to collect photons from trapped ions and form a diffraction-limited image on a camera in order to observe the trapped ions.
Energy storage phosphors @ Phosphor Global Summit 2019Philippe Smet
Presentation on opportunities and limitations of energy storage phosphors, which can be used for glow-in-the-dark roads or safety illumination. Loss mechanisms in phosphors. Presented at the Phosphor Global Summit and Quantum Dot Forum 2019 in San Diego, La Jolla, California. March 19-21.
Pfsmet amazing rise of solid state lightingPhilippe Smet
Overview of lighting technologies. Focus on blue LEDs, solid state lighting, colour conversion by luminescent materials. Applications of LEDs. Future of lighting.
Spectroscopic methods in Inorganic ChemistryChris Sonntag
This document provides an overview of spectroscopic methods in inorganic chemistry, focusing on infrared (IR) spectroscopy. It discusses key concepts like dipole moments, factors that influence bond vibrational frequencies, and using symmetry to determine vibration modes. Specific applications covered include identifying functional groups, distinguishing between cis and trans transition metal carbonyl complexes using IR spectra, and analyzing metal-ligand vibrations in complexes. The document also lists several online resources for IR spectral simulation, prediction, and reference databases.
Space Radiation Superconductive Shield (SR2S) is an EU funded FP7 project which is researching new technology to protect astronauts in space from radiation. On 9th April 2014 in Torino, Italy, SR2S held their first conference to give an update on the project so far.
For more information visit:
www.sr2s.eu
Twitter - @SR2SMars
Multi-channel Detector Readout Integrated Circuits with ADCs for X-ray and Ga...Gunnar Maehlum
The document describes a family of multi-channel readout integrated circuits (ROICs) developed for X-ray and gamma-ray spectroscopy in space applications. The ROICs called VATAs integrate pre-amplifiers, pulse shaping circuits, discriminators, and 10-bit analog-to-digital converters for each of their 32-64 channels. They deliver digital pulse amplitudes and pixel addresses with low power consumption of 0.2-1.3 mW per channel. The VATAs are being used on several space missions including Astro-H, BepiColombo, and FOXSI to perform radiation detection and spectroscopy of high-energy photons. Test results show the ASICs achieve good energy resolution and low
Describe the Schroedinger wavefunctions and energies of electrons in an atom leading to the 3 quantum numbers. These can be also observed in the line spectra of atoms.
Space Radiation Superconductive Shield (SR2S) is an EU funded FP7 project which is researching new technology to protect astronauts in space from radiation. On 9th April 2014 in Torino, Italy, SR2S held their first conference to give an update on the project so far.
For more information visit:
www.sr2s.eu
Twitter - @SR2SMars
Space Radiation Superconductive Shield (SR2S) is an EU funded FP7 project which is researching new technology to protect astronauts in space from radiation. On 9th April 2014 in Torino, Italy, SR2S held their first conference to give an update on the project so far.
For more information visit:
www.sr2s.eu
Twitter - @SR2SMars
1) The electronic structure at oxide interfaces like LaAlO3/SrTiO3 involves an "electronic reconstruction" where a high mobility 2D electron gas forms at the interface between the insulating oxides.
2) DFT calculations using LDA+U show that the polar catastrophe that would occur due to the alternating charged layers in LaAlO3 can be avoided through a distortion of the LaO plane and displacement of the AlO2 plane.
3) Scanning tunneling spectroscopy measurements on LaAlO3/SrTiO3 interfaces match well with the DFT-calculated density of states, confirming the 3d character of the conducting electrons.
Daniel adrien franco lespinasse - status of magnetron sputtered qwrthinfilmsworkshop
The objective of this research is the deposition of a superconductive thin film onto copper Quarter Wave Resonator cavities that can be used in the HIE-ISOLDE facility at CERN. To do this, it was developed an innovative magnetron configuration source. Our experience has shown the efficiency of this particular configuration in order to deposit a uniform thin film, and also improve the superconductive properties of the niobium (Residual Resistance Ratio and Critical Temperature). This presentation presents the recent improvement of the niobium thin film properties and the procedure used to deposit and measure the first resonator at LNL of HIE-ISOLDE type.
Defects in energy storage phosphors: friends or enemies? (PRE19 workshop)Philippe Smet
Plenary talk presented at the PRE19 workshop (Photoluminescence in Rare Earths: Photonic Materials and Devices) in Nice, France, on September 4. Dealing with persistent luminescence, afterglow, mechanoluminescence, traps, defects and thermoluminescence. Overview of the activities of the LumiLab research in the past 10 years.
ICL2017 Counting the photons - persistent phosphorsPhilippe Smet
Talk "Squeezing the energy out of the traps" presented at the 18th International Conference on Luminescence (ICL), August 31 2017. Describes a validated method to estimate the number of traps in storage phosphors, by embedding the phosphor in a polymer layer and counting the emitted photons during the afterglow decay. Work performed at LumiLab (Ghent University) and Concordia University.
Direct/indirect band gap and exciton dispersion: Monolayer and bulk hexagonal...Claudio Attaccalite
1) A tight-binding model for excitons in 2D and layered hexagonal boron nitride provides insight into its optical properties in the bulk and different polymorphs.
2) Ab initio calculations show the flattening of the exciton dispersion in bulk hBN leads to a mixing of direct and indirect transitions, consistently explaining conflicting data on band structure and optical spectra.
3) The model predicts an even stronger direct gap behavior for Bernal stacked hBN, despite it having an indirect fundamental gap.
This document discusses modeling magnetic fields of microtrap arrays for trapping ultracold atoms. It describes how double-loop microtraps can be used to create arrays of traps and transfer atoms between adjacent traps by varying currents. Adding an additional Ioffe coil can generate a trap with a nonzero minimum field to prevent atom loss due to spin flips. The microtraps use much smaller currents than macroscopic traps and allow controlling trap position and depth through bias fields, which could enable applications in precision measurements, quantum information processing, and more.
EMRS 2018 Replacing rare earth ions in LEDs (?)Philippe Smet
Two decades after the development of the blue light-emitting diode (LED), LEDs have quickly established themselves as the lighting technology of the future. The high efficiency, spectral tunability, lack of toxic compounds and a small footprint makes them far more attractive than other lighting technologies. The high efficiency, now well exceeding 100 lum/W in commercial products, has still the margin to double, promising a strong reduction in electricity consumption.
White LEDs are commonly based on a blue LED, combined with luminescent materials, or phosphors, which convert part of the blue light to longer wavelengths, the mixture providing white light. Besides the workhorse Y3Al5O12:Ce (YAG:Ce, yielding yellow emission), europium doped phosphors are used to provide e.g. the red emission required for warm-white LEDs.
Six main requirements for LED phosphors are discussed and used to explain the discrepancy between the high number of compositions described in literature and the handful of actually used compounds, being almost uniquely based on rare earth ions as luminescent center [1]. Alternative materials avoiding the use of rare earth ions are discussed, including Mn4+ doped fluorides phosphors (e.g. K2SiF6:Mn4+ [2]) and quantum dots. Finally, the impact of phosphor geometries on phosphor use, including remote phosphor applications, are discussed.
[1] Smet PF and Joos JJ, Nat. Mater. 16 (2017) 500.
[2] Sijbom H et al, Opt. Mater. Exp. 7 (2017) 3332.
1) When metal nanoparticles are excited by light, they exhibit localized surface plasmon resonance (LSPR) which enhances the local electric field. This study investigates how gold nanoparticles with silica shells of different thicknesses influence the photoluminescence of nearby quantum dots (QDs).
2) Time-resolved fluorescence and photon correlation measurements show that QDs near gold nanoparticles with thinner silica shells have higher biexciton emission quantum yields compared to QDs on glass.
3) Electrodynamics modeling suggests that the enhanced local electric field and additional non-radiative energy transfer from QDs to gold nanoparticles impact exciton and biexciton emission intensities and lifetimes in a way that increases the bi
Low energy ion beam nanopatterning of CoxSi1-x Surfaces -Thesis Defense seminarDr. Basanta Kumar Parida
The document summarizes a defense seminar presentation on low energy ion beam nanopatterning of CoxSi1-x surfaces. It discusses various topics related to ion beam nanopatterning including experimental aspects, the effect of ion energy and fluence on morphology, the influence of ion species and incidence angle, and theoretical modeling. It provides details on the deposition of CoxSi1-x films, the ion irradiation experimental setup using different ion sources, and characterization techniques. Morphological transitions from ripples to dots are observed with increasing ion energy or decreasing fluence. Ion species and incidence angle are also found to influence pattern morphology.
This document summarizes work towards developing a quantum memory for non-classical light using cold atoms. It discusses generating squeezed vacuum light compatible with an atomic memory using an optical parametric oscillator. The light is characterized and techniques for interfacing it with the memory are explored. This includes creating two atomic ensembles for memory applications and characterizing their properties like storage time and efficiency. The goal is to eventually entangle the two memory ensembles.
Machine learning approaches are being applied in several ways to 21cm cosmology studies of the Epoch of Reionization (EoR):
1) Neural networks are used as emulators to rapidly predict 21cm power spectra from astrophysical parameters, speeding up Markov chain Monte Carlo parameter estimation.
2) Neural networks are trained on simulated 21cm power spectra to directly estimate astrophysical parameters, bypassing computationally expensive simulations.
3) Convolutional neural networks classify 21cm images to distinguish different sources driving reionization or compress image data into lower-dimensional summaries for likelihood-free inference of parameters.
Machine learning techniques are increasingly being used to tackle the statistical challenges of analyzing upcoming 21cm data and
I gave 1 hour seminar at ANSTO (Australian Nuclear Science and Technology Organization) to introduce my approach to magnetism. I see myself as an experimental physicist who is studying magnetism by using neutron scattering techniques. Throughout my career, I had learned local structure analysis (PDF), magnetic structural analysis, and inelastic neutron scattering technique to investigate superconductor, multiferroics, antiferromagnets, helimagnets, and frustrated magnets. I was trying to explain my approach to magnetism as an experiment physicist to both professional scientists and novices.
Role of excitonic effects in nonlinear optical properties of 2D materialsClaudio Attaccalite
The document discusses the role of excitonic effects in nonlinear optical properties of 2D materials. It presents a real-time approach to calculate nonlinear optics that includes excitonic effects using a dynamical polarization consistent with periodic boundary conditions. Calculations show excitonic effects enhance second harmonic generation at resonant energies in materials like MoS2 and h-BN. Excitonic effects also impact third harmonic generation by redistributing intensity and reducing it at resonant energies. The approach is implemented in an open source nonlinear optics module.
This group is working to develop the systems needed to trap and laser cool barium and lanthanum ions for use in quantum information experiments. They have:
1) Built a cavity to frequency double infrared laser light to 490nm blue light needed to laser cool barium ions. They achieved 74.43μW of 490nm light from 72mW of infrared input.
2) Modeled an ion trap and determined voltages that can stably trap lanthanum ions while ejecting contaminant lanthanum ions.
3) Designed an imaging system using multiple lenses to collect photons from trapped ions and form a diffraction-limited image on a camera in order to observe the trapped ions.
Energy storage phosphors @ Phosphor Global Summit 2019Philippe Smet
Presentation on opportunities and limitations of energy storage phosphors, which can be used for glow-in-the-dark roads or safety illumination. Loss mechanisms in phosphors. Presented at the Phosphor Global Summit and Quantum Dot Forum 2019 in San Diego, La Jolla, California. March 19-21.
Pfsmet amazing rise of solid state lightingPhilippe Smet
Overview of lighting technologies. Focus on blue LEDs, solid state lighting, colour conversion by luminescent materials. Applications of LEDs. Future of lighting.
Spectroscopic methods in Inorganic ChemistryChris Sonntag
This document provides an overview of spectroscopic methods in inorganic chemistry, focusing on infrared (IR) spectroscopy. It discusses key concepts like dipole moments, factors that influence bond vibrational frequencies, and using symmetry to determine vibration modes. Specific applications covered include identifying functional groups, distinguishing between cis and trans transition metal carbonyl complexes using IR spectra, and analyzing metal-ligand vibrations in complexes. The document also lists several online resources for IR spectral simulation, prediction, and reference databases.
Space Radiation Superconductive Shield (SR2S) is an EU funded FP7 project which is researching new technology to protect astronauts in space from radiation. On 9th April 2014 in Torino, Italy, SR2S held their first conference to give an update on the project so far.
For more information visit:
www.sr2s.eu
Twitter - @SR2SMars
Multi-channel Detector Readout Integrated Circuits with ADCs for X-ray and Ga...Gunnar Maehlum
The document describes a family of multi-channel readout integrated circuits (ROICs) developed for X-ray and gamma-ray spectroscopy in space applications. The ROICs called VATAs integrate pre-amplifiers, pulse shaping circuits, discriminators, and 10-bit analog-to-digital converters for each of their 32-64 channels. They deliver digital pulse amplitudes and pixel addresses with low power consumption of 0.2-1.3 mW per channel. The VATAs are being used on several space missions including Astro-H, BepiColombo, and FOXSI to perform radiation detection and spectroscopy of high-energy photons. Test results show the ASICs achieve good energy resolution and low
Describe the Schroedinger wavefunctions and energies of electrons in an atom leading to the 3 quantum numbers. These can be also observed in the line spectra of atoms.
Space Radiation Superconductive Shield (SR2S) is an EU funded FP7 project which is researching new technology to protect astronauts in space from radiation. On 9th April 2014 in Torino, Italy, SR2S held their first conference to give an update on the project so far.
For more information visit:
www.sr2s.eu
Twitter - @SR2SMars
Space Radiation Superconductive Shield (SR2S) is an EU funded FP7 project which is researching new technology to protect astronauts in space from radiation. On 9th April 2014 in Torino, Italy, SR2S held their first conference to give an update on the project so far.
For more information visit:
www.sr2s.eu
Twitter - @SR2SMars
1) The electronic structure at oxide interfaces like LaAlO3/SrTiO3 involves an "electronic reconstruction" where a high mobility 2D electron gas forms at the interface between the insulating oxides.
2) DFT calculations using LDA+U show that the polar catastrophe that would occur due to the alternating charged layers in LaAlO3 can be avoided through a distortion of the LaO plane and displacement of the AlO2 plane.
3) Scanning tunneling spectroscopy measurements on LaAlO3/SrTiO3 interfaces match well with the DFT-calculated density of states, confirming the 3d character of the conducting electrons.
Daniel adrien franco lespinasse - status of magnetron sputtered qwrthinfilmsworkshop
The objective of this research is the deposition of a superconductive thin film onto copper Quarter Wave Resonator cavities that can be used in the HIE-ISOLDE facility at CERN. To do this, it was developed an innovative magnetron configuration source. Our experience has shown the efficiency of this particular configuration in order to deposit a uniform thin film, and also improve the superconductive properties of the niobium (Residual Resistance Ratio and Critical Temperature). This presentation presents the recent improvement of the niobium thin film properties and the procedure used to deposit and measure the first resonator at LNL of HIE-ISOLDE type.
Defects in energy storage phosphors: friends or enemies? (PRE19 workshop)Philippe Smet
Plenary talk presented at the PRE19 workshop (Photoluminescence in Rare Earths: Photonic Materials and Devices) in Nice, France, on September 4. Dealing with persistent luminescence, afterglow, mechanoluminescence, traps, defects and thermoluminescence. Overview of the activities of the LumiLab research in the past 10 years.
ICL2017 Counting the photons - persistent phosphorsPhilippe Smet
Talk "Squeezing the energy out of the traps" presented at the 18th International Conference on Luminescence (ICL), August 31 2017. Describes a validated method to estimate the number of traps in storage phosphors, by embedding the phosphor in a polymer layer and counting the emitted photons during the afterglow decay. Work performed at LumiLab (Ghent University) and Concordia University.
Direct/indirect band gap and exciton dispersion: Monolayer and bulk hexagonal...Claudio Attaccalite
1) A tight-binding model for excitons in 2D and layered hexagonal boron nitride provides insight into its optical properties in the bulk and different polymorphs.
2) Ab initio calculations show the flattening of the exciton dispersion in bulk hBN leads to a mixing of direct and indirect transitions, consistently explaining conflicting data on band structure and optical spectra.
3) The model predicts an even stronger direct gap behavior for Bernal stacked hBN, despite it having an indirect fundamental gap.
This document discusses modeling magnetic fields of microtrap arrays for trapping ultracold atoms. It describes how double-loop microtraps can be used to create arrays of traps and transfer atoms between adjacent traps by varying currents. Adding an additional Ioffe coil can generate a trap with a nonzero minimum field to prevent atom loss due to spin flips. The microtraps use much smaller currents than macroscopic traps and allow controlling trap position and depth through bias fields, which could enable applications in precision measurements, quantum information processing, and more.
EMRS 2018 Replacing rare earth ions in LEDs (?)Philippe Smet
Two decades after the development of the blue light-emitting diode (LED), LEDs have quickly established themselves as the lighting technology of the future. The high efficiency, spectral tunability, lack of toxic compounds and a small footprint makes them far more attractive than other lighting technologies. The high efficiency, now well exceeding 100 lum/W in commercial products, has still the margin to double, promising a strong reduction in electricity consumption.
White LEDs are commonly based on a blue LED, combined with luminescent materials, or phosphors, which convert part of the blue light to longer wavelengths, the mixture providing white light. Besides the workhorse Y3Al5O12:Ce (YAG:Ce, yielding yellow emission), europium doped phosphors are used to provide e.g. the red emission required for warm-white LEDs.
Six main requirements for LED phosphors are discussed and used to explain the discrepancy between the high number of compositions described in literature and the handful of actually used compounds, being almost uniquely based on rare earth ions as luminescent center [1]. Alternative materials avoiding the use of rare earth ions are discussed, including Mn4+ doped fluorides phosphors (e.g. K2SiF6:Mn4+ [2]) and quantum dots. Finally, the impact of phosphor geometries on phosphor use, including remote phosphor applications, are discussed.
[1] Smet PF and Joos JJ, Nat. Mater. 16 (2017) 500.
[2] Sijbom H et al, Opt. Mater. Exp. 7 (2017) 3332.
1) When metal nanoparticles are excited by light, they exhibit localized surface plasmon resonance (LSPR) which enhances the local electric field. This study investigates how gold nanoparticles with silica shells of different thicknesses influence the photoluminescence of nearby quantum dots (QDs).
2) Time-resolved fluorescence and photon correlation measurements show that QDs near gold nanoparticles with thinner silica shells have higher biexciton emission quantum yields compared to QDs on glass.
3) Electrodynamics modeling suggests that the enhanced local electric field and additional non-radiative energy transfer from QDs to gold nanoparticles impact exciton and biexciton emission intensities and lifetimes in a way that increases the bi
Low energy ion beam nanopatterning of CoxSi1-x Surfaces -Thesis Defense seminarDr. Basanta Kumar Parida
The document summarizes a defense seminar presentation on low energy ion beam nanopatterning of CoxSi1-x surfaces. It discusses various topics related to ion beam nanopatterning including experimental aspects, the effect of ion energy and fluence on morphology, the influence of ion species and incidence angle, and theoretical modeling. It provides details on the deposition of CoxSi1-x films, the ion irradiation experimental setup using different ion sources, and characterization techniques. Morphological transitions from ripples to dots are observed with increasing ion energy or decreasing fluence. Ion species and incidence angle are also found to influence pattern morphology.
This document summarizes work towards developing a quantum memory for non-classical light using cold atoms. It discusses generating squeezed vacuum light compatible with an atomic memory using an optical parametric oscillator. The light is characterized and techniques for interfacing it with the memory are explored. This includes creating two atomic ensembles for memory applications and characterizing their properties like storage time and efficiency. The goal is to eventually entangle the two memory ensembles.
Machine learning approaches are being applied in several ways to 21cm cosmology studies of the Epoch of Reionization (EoR):
1) Neural networks are used as emulators to rapidly predict 21cm power spectra from astrophysical parameters, speeding up Markov chain Monte Carlo parameter estimation.
2) Neural networks are trained on simulated 21cm power spectra to directly estimate astrophysical parameters, bypassing computationally expensive simulations.
3) Convolutional neural networks classify 21cm images to distinguish different sources driving reionization or compress image data into lower-dimensional summaries for likelihood-free inference of parameters.
Machine learning techniques are increasingly being used to tackle the statistical challenges of analyzing upcoming 21cm data and
I gave 1 hour seminar at ANSTO (Australian Nuclear Science and Technology Organization) to introduce my approach to magnetism. I see myself as an experimental physicist who is studying magnetism by using neutron scattering techniques. Throughout my career, I had learned local structure analysis (PDF), magnetic structural analysis, and inelastic neutron scattering technique to investigate superconductor, multiferroics, antiferromagnets, helimagnets, and frustrated magnets. I was trying to explain my approach to magnetism as an experiment physicist to both professional scientists and novices.
The presentation file on workshop on Neutron and X-ray Characterisation on Caloric Materials, introduction to neutron scattering experiment with triple axis spectrometer for material scientist
This document summarizes a presentation about exploring the early universe using the neutral hydrogen 21cm line. It discusses:
1. The history of the universe from the dark ages to the epoch of reionization, when the first stars and galaxies formed.
2. Current observations of the epoch of reionization provide constraints on the global neutral hydrogen fraction over time but do not reveal detailed spatial information.
3. Observing the 21cm line from neutral hydrogen in the intergalactic medium could directly probe the epoch of reionization and reveal information about ionized bubble morphology, the first luminous objects, and galaxy formation.
This document provides information about the "Raman and Luminescence Submicron Spectroscopy" Laboratory located at the V. Lashkaryov Institute of Semiconductor Physics, National Academy of Science, Ukraine. The laboratory contains several lasers, spectrometers, microscopes, and temperature control equipment used to perform Raman and luminescence spectroscopy and mapping on semiconductor nanostructures with submicron spatial resolution. The laboratory studies properties such as chemical composition, strain, temperature, carrier mobility and concentration in nanostructures for applications in microelectronics and optoelectronics. Team members and their areas of research interest are also listed.
The document summarizes information about the Sun and discusses several particle physics experiments related to the Sun. It provides basic facts about the Sun such as its temperature, age, composition and total luminosity. It then discusses three specific topics - solar neutrinos, solar axions, and WIMPs in relation to the Sun. For solar neutrinos, it explains their production through the pp-chain and CNO cycle and discusses several past experiments that detected solar neutrinos such as Homestake, SAGE, GALLEX, Kamiokande and Super-Kamiokande, and SNO. It notes the "solar neutrino problem" of a discrepancy between predicted and observed solar neutrino fluxes. For solar axions, it defines what
The document discusses exploring the early universe using the neutral hydrogen 21cm line. It provides an overview of Hayato Shimabukuro's background and research interests, which include 21cm cosmology and analyzing 21cm signals with machine learning. The presentation outlines the basics of the 21cm line, the current status of 21cm cosmology experiments, and challenges in the field. It also describes work using artificial neural networks to estimate reionization parameters from 21cm power spectra and recover bubble size distributions from 21cm observations.
The Evolution of Elliptical Galaxies in Rich ClustersRobert Berrington
This document summarizes research on the properties of early-type galaxies in rich galaxy clusters. It finds that rich clusters contain thousands of galaxies and have masses of around 1015 solar masses, while poor clusters contain hundreds of galaxies with masses of around 1014 solar masses. The physics of cluster mergers is driven by gravitational forces, with the total gravitational energy available during a merger calculated based on the masses and velocities of the merging clusters. Mergers can create shocks that accelerate particles and produce radio halos and relics detectable by radio and gamma-ray observatories. The properties of the Coma Cluster, a likely ongoing three-body merger, are modeled to study nonthermal particle acceleration and radiation from the merger.
The new approach provides practical considerations for selection of the elements and their isotopes suitable for cold fusion energy and minimization of the radioactive waste.
Satellite RF Communications and Onboard Processing Course SamplerJim Jenkins
Successful systems engineering requires a broad understanding of the important principles of modern satellite communications and onboard data processing. This course covers both theory and practice, with emphasis on the important system engineering principles, tradeoffs, and rules of thumb. The latest technologies are covered, including those needed for constellations of satellites.
This course is recommended for engineers and scientists interested in acquiring an understanding of satellite communications, command and telemetry, onboard computing, and tracking. Each participant will receive a complete set of notes.
This document describes the analysis of high-quality X-ray spectra of Mrk 509 taken with the Reflection Grating Spectrometers on XMM-Newton. The spectra were obtained using a new multi-pointing mode over 600 ks to constrain properties of the outflow. Combining the individual spectra required developing new methods to account for gaps in the data from detector issues. Absorption lines in the spectra were analyzed to study the outflow.
Observing ultra-high energy cosmic rays with prototypes of the Fluorescence d...Toshihiro FUJII
1. The document describes observations of ultra-high energy cosmic rays using prototypes of the Fluorescence detector Array of Single-pixel Telescopes (FAST) project in both hemispheres.
2. FAST aims to observe cosmic rays with energies over 10^20 eV using an array of low-cost telescopes to cover a large ground area.
3. Initial results are presented from FAST prototypes installed at the Telescope Array site, including coincident observations of air showers with the Telescope Array fluorescence detector and reconstruction of shower parameters from FAST data.
This document discusses various techniques for crystal structure analysis using diffraction methods, including X-ray diffraction, electron diffraction, and neutron diffraction. It provides background on the essential physics of Bragg diffraction and scattering. Key topics covered include generating X-rays, basic diffractometer setups, powder and thin film diffraction techniques, and applications such as phase identification and structure determination.
ppt on the Solar cells understanding semiconductor devicesYuvraj Singh
1. The document provides an overview of semiconductor devices including solar cells, LEDs, transistors, and more through a schedule and explanations of key concepts.
2. The core concepts covered include how solar cells work through photovoltaic absorption, charge carrier generation and transport, and collection.
3. Different types of solar cell materials and designs are examined like silicon, CIGS thin films, and multi-junction cells to understand how their properties influence efficiency.
Magnets are key components of particle accelerators. Their modeling involves several stages including simple hard-edge models for initial design, detailed computer calculations, mechanical/electrical design and construction, measurement of field profiles, and beam testing. Magnet measurements are performed using devices like gaussmeters and rotating coils to characterize fields and multipoles. Effective magnet lengths are important parameters and may differ from physical lengths for devices with non-uniform field profiles.
The document summarizes the PAMELA experiment's silicon tracker, including its design, components, performance, and preliminary analysis of flight data. The tracker uses silicon microstrip sensors and VA1 readout chips to precisely measure particle trajectories in the magnetic spectrometer. Initial flight data shows the tracker is working as expected, with nominal noise levels, signal-to-noise ratios, and spatial resolution allowing for momentum and charge identification of cosmic rays.
This document discusses the scientific opportunity of measuring prompt optical emission from gamma-ray bursts (GRBs) in order to better understand GRB emission mechanisms. It proposes a new instrument capable of simultaneous multi-color optical and infrared observations of GRBs with high time resolution. Such an instrument could measure prompt optical light curves and spectra, test models of GRB emission, and probe properties of dust around GRBs.
Study of a transient plasma process in lightning using the BSM-SG models of a...Stoyan Sarg Sargoytchev
1) The document describes an international conference on nanotechnology and materials science held from July 22-24 in Rome.
2) It discusses Stoyan Sarg's work analyzing lightning using the BSM-SG theory of atoms and particles, including suggesting a laboratory experiment to study lightning.
3) Sarg's work uses experimental data from various fields to reveal the substructure of elementary particles and atomic nuclei according to the BSM-SG theory.
Similar to Young Scientist Award in JPS (invited talk) (20)
The debris of the ‘last major merger’ is dynamically youngSérgio Sacani
The Milky Way’s (MW) inner stellar halo contains an [Fe/H]-rich component with highly eccentric orbits, often referred to as the
‘last major merger.’ Hypotheses for the origin of this component include Gaia-Sausage/Enceladus (GSE), where the progenitor
collided with the MW proto-disc 8–11 Gyr ago, and the Virgo Radial Merger (VRM), where the progenitor collided with the
MW disc within the last 3 Gyr. These two scenarios make different predictions about observable structure in local phase space,
because the morphology of debris depends on how long it has had to phase mix. The recently identified phase-space folds in Gaia
DR3 have positive caustic velocities, making them fundamentally different than the phase-mixed chevrons found in simulations
at late times. Roughly 20 per cent of the stars in the prograde local stellar halo are associated with the observed caustics. Based
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We also compare the observed phase-space distribution to FIRE-2 Latte simulations of GSE-like mergers, using a quantitative
measurement of phase mixing (2D causticality). The observed local phase-space distribution best matches the simulated data
1–2 Gyr after collision, and certainly not later than 3 Gyr. This is further evidence that the progenitor of the ‘last major merger’
did not collide with the MW proto-disc at early times, as is thought for the GSE, but instead collided with the MW disc within
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Describing and Interpreting an Immersive Learning Case with the Immersion Cub...Leonel Morgado
Current descriptions of immersive learning cases are often difficult or impossible to compare. This is due to a myriad of different options on what details to include, which aspects are relevant, and on the descriptive approaches employed. Also, these aspects often combine very specific details with more general guidelines or indicate intents and rationales without clarifying their implementation. In this paper we provide a method to describe immersive learning cases that is structured to enable comparisons, yet flexible enough to allow researchers and practitioners to decide which aspects to include. This method leverages a taxonomy that classifies educational aspects at three levels (uses, practices, and strategies) and then utilizes two frameworks, the Immersive Learning Brain and the Immersion Cube, to enable a structured description and interpretation of immersive learning cases. The method is then demonstrated on a published immersive learning case on training for wind turbine maintenance using virtual reality. Applying the method results in a structured artifact, the Immersive Learning Case Sheet, that tags the case with its proximal uses, practices, and strategies, and refines the free text case description to ensure that matching details are included. This contribution is thus a case description method in support of future comparative research of immersive learning cases. We then discuss how the resulting description and interpretation can be leveraged to change immersion learning cases, by enriching them (considering low-effort changes or additions) or innovating (exploring more challenging avenues of transformation). The method holds significant promise to support better-grounded research in immersive learning.
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(June 12, 2024) Webinar: Development of PET theranostics targeting the molecu...Scintica Instrumentation
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The binding of cosmological structures by massless topological defectsSérgio Sacani
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Authoring a personal GPT for your research and practice: How we created the Q...Leonel Morgado
Thematic analysis in qualitative research is a time-consuming and systematic task, typically done using teams. Team members must ground their activities on common understandings of the major concepts underlying the thematic analysis, and define criteria for its development. However, conceptual misunderstandings, equivocations, and lack of adherence to criteria are challenges to the quality and speed of this process. Given the distributed and uncertain nature of this process, we wondered if the tasks in thematic analysis could be supported by readily available artificial intelligence chatbots. Our early efforts point to potential benefits: not just saving time in the coding process but better adherence to criteria and grounding, by increasing triangulation between humans and artificial intelligence. This tutorial will provide a description and demonstration of the process we followed, as two academic researchers, to develop a custom ChatGPT to assist with qualitative coding in the thematic data analysis process of immersive learning accounts in a survey of the academic literature: QUAL-E Immersive Learning Thematic Analysis Helper. In the hands-on time, participants will try out QUAL-E and develop their ideas for their own qualitative coding ChatGPT. Participants that have the paid ChatGPT Plus subscription can create a draft of their assistants. The organizers will provide course materials and slide deck that participants will be able to utilize to continue development of their custom GPT. The paid subscription to ChatGPT Plus is not required to participate in this workshop, just for trying out personal GPTs during it.
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The cost of acquiring information by natural selectionCarl Bergstrom
This is a short talk that I gave at the Banff International Research Station workshop on Modeling and Theory in Population Biology. The idea is to try to understand how the burden of natural selection relates to the amount of information that selection puts into the genome.
It's based on the first part of this research paper:
The cost of information acquisition by natural selection
Ryan Seamus McGee, Olivia Kosterlitz, Artem Kaznatcheev, Benjamin Kerr, Carl T. Bergstrom
bioRxiv 2022.07.02.498577; doi: https://doi.org/10.1101/2022.07.02.498577
ESA/ACT Science Coffee: Diego Blas - Gravitational wave detection with orbita...Advanced-Concepts-Team
Presentation in the Science Coffee of the Advanced Concepts Team of the European Space Agency on the 07.06.2024.
Speaker: Diego Blas (IFAE/ICREA)
Title: Gravitational wave detection with orbital motion of Moon and artificial
Abstract:
In this talk I will describe some recent ideas to find gravitational waves from supermassive black holes or of primordial origin by studying their secular effect on the orbital motion of the Moon or satellites that are laser ranged.
2. 2
Footprints
2011-2014 Two-species atomic BEC
@ Inouye lab., UTokyo (currently in Osaka City Univ.)
2014-2017 Cavity optomagnonics
@ Nakamura-Usami lab., RCAST, UTokyo
2017-2019 QD + photonic crystal cavity
@ Arakawa-Iwamoto lab., IIS, Utokyo
2019- Hybrid quantum systems
@ Komaba Institute for Science, UTokyo
(先進科学研究機構)
Ion trap with vertically integrated cavity
@ JST PRESTO
← “Alto Osada”で画像検索すると真っ先に出てくる…
3. 3
Indices
• Cavity optomagnonics?
• Magnon-Brillouin scattering and puzzles
• Physics of cavity-optomagnonics system
• Cavity optomagnonics and magnetic textures
• Summary, acknowledgements and ads
4. 4
Optomagnonics
T. Satoh et al. Nature Photon. 6, 662 (2012) T. Satoh et al. Nature Photon. 9, 25 (2014)
S. O. Demokritov et al. Nature 443, 430 (2006) R. Hisatomi, AO et. al., PRB (2016)
Interaction is weak (spin-orbit coupling)
Enhancement by an optical cavity
Cavity optomagnonics
Condensed
matter physics
Quantum
electronics
5. 5
Possible applications
Y. Tabuchi et. al., Science (2015)
SC qubit magnon
10 GHz
microwave
200 THz
light
Microwave-to-optical photon converter
I. Zutic and H. Dery Nature Materials 10, 647
Opto-spintronics Chiral photonics
I. Sollner et al.,Nature Nanotech. 10, 775
6. 6
Al2O3 rod
1 mm
Yttrium iron garnet (YIG) sphere
Transparent
for 1.5 µm light
Ferrimagnetic
Whispering gallery modes
(WGMs)
Walker modes
A. Gloppe et al,. PRApplied 12, 014061 (2019).
magnon-Brillouin
scattering
7. 7
Indices
• Cavity optomagnonics?
• Magnon-Brillouin scattering and puzzles
• Physics of cavity-optomagnonics system
• Cavity optomagnonics and magnetic textures
• Summary, acknowledgements and ads
8. Whispering gallery mode (WGM)
• Resonance: 2𝜋𝑅 ⋅ 𝑛r = 𝑚𝜆
(𝑚 ∈ ℤ)
• Geometrical birefringence
𝑓TE
𝑚
< 𝑓TM
𝑚
8
𝑚 − 1 𝑚 𝑚 𝑚 + 1 𝑚 + 1
Red = TM Blue = TE
Mode index
Frequency
Transverse
Magnetic
Transverse
Electric
𝑓TM
𝑚
− 𝑓TE
𝑚
25. 26
Indices
• Cavity optomagnonics?
• Magnon-Brillouin scattering and puzzles
• Physics of cavity-optomagnonics system
• Cavity optomagnonics and magnetic textures
• Summary, acknowledgements and ads
28. 29
Model
• Single magnon = single-spin flip
|𝑔, 𝑛〉
|𝑔, 𝑛 + 1〉
|𝑒, 𝑛〉
|𝑒, 𝑛 + 1〉
|𝑒, 𝑛 − 1〉
|𝑔, 𝑛 − 1〉
𝜎−
𝜎+ 𝜋
𝜋
𝜎+
𝜎−
𝑔/𝑒, 𝑛 = |electronic state, number of magnons〉
Magnetic field
29. 30
Polarizations of WGMs
Magnetic field
= 𝜋 polarization
= 𝜎+ and 𝜎− polarizations
Spin-Hall effect of light
M. Onoda et al., PRL 93, 083901 (2004).
“Rays of the two (transverse) spin components
shift”
~ 4 µm
34. 36
Indices
• Cavity optomagnonics?
• Magnon-Brillouin scattering and puzzles
• Physics of cavity-optomagnonics system
• Cavity optomagnonics and magnetic textures
• Summary, acknowledgements and ads
40. 3𝑔Kittel 12𝑔Kittel2𝑔Kittel𝑔Kittel
42
Nonreciprocal Brillouin scattering
0 2 0 1
Different OAM of magnon reciprocal/non-.
Interplay with spin-Hall effect of WGM!
[AO et al., PRL 116, 223601 (2016).]
[AO et al., PRL 120, 133602 (2018).]
[AO et al., NJP 20, 103018 (2018).]
41. 43
Indices
• Cavity optomagnonics?
• Magnon-Brillouin scattering and puzzles
• Physics of cavity-optomagnonics system
• Cavity optomagnonics and magnetic textures
• Summary, acknowledgements and ads
• (時間が余ったら)博士取得後の珍事
42. 44
Summary
• Brillouin scatterings of WGM light by Walker
modes were investigated
• OAM of magnon and photon result in
nontrivial reciprocal/nonreciprocal Brillouin
scattering
• Cavity enhancement of the Brillouin scattering
was examined K. Usami Y. Nakamura
Great thanks to
all the co-workers!
43. 45
Recent activities in Usami’s group
Induction tomography
of
Walker modes
A. Gloppe et al.,
arXiv:1809.09785
• Two-magnon process
• “Bizarre” Brillouin
scattering
- Umklapp process joins
- Looks like spin non-
conserving!
R. Hisatomi et
al.,
arXiv:1905.0401
8
Magnonic
crystal
S. Baba et al.,
arXiv:1905.0468
3
Thank you for the kind introduction and I am grateful to the organizers who invited me o such a celebrated, awesome conference. Here I will talk about the cavity optomagnonics with quasivortices which was one of the topics I dealt with in my PhD study.
Well we should first note that there are a numerous number of works aiming at controlling spin waves or its quantum, magnon, by electromagnetic waves. By microwave it’s been done from long ago, and current topic is to address or detect magnons by optical means, to access the k-space information held by the magnon. However, it’s quite hard. Quite hard because the light-magnon interaction is inevitably mediated by the spin-orbit interaction of the electron in the material. Our idea was to enhance this inherently weak interaction using the optical cavity. That’s the idea of cavity optomagnonics, which has the same spirit as the cavity optomechanics.
Well we should first note that there are a numerous number of works aiming at controlling spin waves or its quantum, magnon, by electromagnetic waves. By microwave it’s been done from long ago, and current topic is to address or detect magnons by optical means, to access the k-space information held by the magnon. However, it’s quite hard. Quite hard because the light-magnon interaction is inevitably mediated by the spin-orbit interaction of the electron in the material. Our idea was to enhance this inherently weak interaction using the optical cavity. That’s the idea of cavity optomagnonics, which has the same spirit as the cavity optomechanics.
The system stimulates us to apply it to the Microwave-to-optical photon converter that can possibly be used to the quantum interface, or some device made up of the combination of spintronic and optical technologies. Another interesting thing is the chiral photonic devices useful for the nanophotonic circuits.
Okay, then given such an idea, we want nice magneto-optical material that makes it feasible. And in most cavity optomagnonics activities the yttrium iron garnet sphere is adopted. It is ferrimagnetic on one hand to exhibit magnetostatic modes of rich spin textures. On the other hand YIG is highly transparent at telecom wavelength and the sphere supports whispering gallery modes. The light can circulate the periphery to form the optical resonance. Here’s the situation we want. Walker mode magnons can be addressed by the optical resonator!
Okay, let’s move on to the experiment. We have a YIG sphere of diameter 1mm and the magnons are excited by the microwave through the loop coil. The excited magnons are in this experiment detected by the WGM light injected evanescently through this prism. Since we are interested in creating or annihilating magnons by light, the Brillouin scattering is concerned here, namely the energy and the angular momenta of the magnon should be transferred to or retracted from the WGM. These facts requires the scattered light to possess the frequency shifted by magnon frequency, about 7 GHz, and the polarization rotated. So here we detect the fluctuation of the output light polarization by the fast photodetector to get the sideband signal at 7 GHz. The optical sideband is beaten down to the microwave regime by taking heterodyne signal. In the network analyzer the simplest, uniform magnetostatic mode, the Kittel mode, is observed as the dip in the reflection signal of the loop coil and the Brillouin-scattered light is detected like this yellow signal.
Okay, let’s move on to the experiment. We have a YIG sphere of diameter 1mm and the magnons are excited by the microwave through the loop coil. The excited magnons are in this experiment detected by the WGM light injected evanescently through this prism. Since we are interested in creating or annihilating magnons by light, the Brillouin scattering is concerned here, namely the energy and the angular momenta of the magnon should be transferred to or retracted from the WGM. These facts requires the scattered light to possess the frequency shifted by magnon frequency, about 7 GHz, and the polarization rotated. So here we detect the fluctuation of the output light polarization by the fast photodetector to get the sideband signal at 7 GHz. The optical sideband is beaten down to the microwave regime by taking heterodyne signal. In the network analyzer the simplest, uniform magnetostatic mode, the Kittel mode, is observed as the dip in the reflection signal of the loop coil and the Brillouin-scattered light is detected like this yellow signal.
What is astonishing is that when the direction of the WGM light is clockwise, indicated by blue, the Brillouin scattering can be observed, however, when counterclockwise, indicated by red, the signal disappears! The phenomenon is nonreciprocal. This is not as usual as simple Faraday effect because the Brillouin scattering is dynamical effect. This nonreciprocity was revealed to be due to the interplay among energy and spin angular momentum conservation, and the spin-orbit coupled nature of the WGM. We do not dive into the great detail in this talk. Let us see further mystery we encountered in the experiment. That is, when you see the higher-order magnons located at the higher frequency, you see the nonreciprocal or reciprocal nature is strongly dependent on those modes.
Let’s take a look at these magnon modes. The leftmost is the Kittel mode, the uniform mode. And others can be identified by checking their frequencies for variable magnetic fields. These are the transverse magnetization distributions and you can see various textures exhibited by these, for example the 401 mode possesses the spiral texture at some instance. What makes these textures different from each other is resolved by examining the winding number of these vector fields. In order to do so we shall track the transverse magnetization in the vicinity of the perimeter.
First, the Kittel mode and 311 mode the transverse magnetization points the same direction all along the circumference, therefore the winding number reads 0.
For the 401 mode, it is up here, rotates by 180 degree on the other side and goes back. The total amount of rotation is 2pi, which yields the winding number of 1.
And for 31bar1 mode, from its pattern we see the magnetization is up here, down here, up, down, up, and rotated all the way by 4pi in total. Thus the winding number is 2.
Since such rotations are the spatial variation of the phase, we can interpret them as the orbital angular momenta.
Okay, then let’s have a look back. Now the orbital angular momenta are assigned to the Walker modes. And we notice that for magnons with vanishing OAM, the clockwise cases are more prominent than the counterclockwise cases. If the magnon have OAM of 1, the Brillouin scattering appears to be reciprocal. If 2, in this case the counterclockwise scattering is superior to the clockwise one. These results are in a quite nice agreement with the theory that take in to account the energy and angular momenta conservation.
Okay, then let’s have a look back. Now the orbital angular momenta are assigned to the Walker modes. And we notice that for magnons with vanishing OAM, the clockwise cases are more prominent than the counterclockwise cases. If the magnon have OAM of 1, the Brillouin scattering appears to be reciprocal. If 2, in this case the counterclockwise scattering is superior to the clockwise one. These results are in a quite nice agreement with the theory that take in to account the energy and angular momenta conservation.
Okay, then let’s have a look back. Now the orbital angular momenta are assigned to the Walker modes. And we notice that for magnons with vanishing OAM, the clockwise cases are more prominent than the counterclockwise cases. If the magnon have OAM of 1, the Brillouin scattering appears to be reciprocal. If 2, in this case the counterclockwise scattering is superior to the clockwise one. These results are in a quite nice agreement with the theory that take in to account the energy and angular momenta conservation.