Gigahertz Ultrasonics in Metamaterials
Event details
| Date | 18.09.2018 |
| Hour | 10:00 |
| Speaker | Prof. Olivier B. Wright, Hokkaido University, Japan |
| Location | |
| Category | Conferences - Seminars |
The Institute of Microengineering (IMT) and the Lausanne Centre for Ultrafast Science (LACUS) are pleased to invite you to the following seminar, hosted by Prof. Yves Bellouard & Prof. Majed Chergui:
Experiments and simulations on both optical and acoustic metamaterials interacting with GHz vibrations are presented. We firstly consider the extraordinary transmission of GHz surface acoustic waves through nanoscale metamaterial structures based on thin resonant bridges, showing how significant improvements in the acoustic transmission can be obtained at specific resonant frequencies. We then present the GHz modulation of the optical extraordinary transmission through a nanoscale hole-array structure, and the GHz modulation of the optical reflection from a split-ring resonator metamaterial that vibrates like an array of tiny tuning forks. Possible applications of this work are in ultrafast modulation and sensing.
Controlling sound or light is essential to a diverse range of applications. Periodic and aperiodic acoustic structures formed of individual acoustic or electromagnetic resonators, under conditions in which the acoustic or optical wavelength is much smaller than the resonator spacing, provide a versatile way to block, absorb, guide or transmit sound or light. Understanding their behaviour has been the focus of much research. Such structures, known as metamaterials, can be constructed from meter to nanometer length scales. We show how, for micron-scale to nanoscale structures, they can be probed using ultrafast optics to generate gigahertz sound fields inside them and be used to modulate optical transmission, or achieve enhanced acoustic transmission. Prospects for applications of GHz acoustic waves in acoustic or optical metamaterials will also be presented.
Bio:
O. B. Wright initially specialized in low temperature solid state physics. During his PhD course he published a detailed account of the thermoelastic effect in glasses at low temperatures—a modern version of a rubber band experiment in which the temperature change of the band is monitored on stretching.
After obtaining an industrial post he concentrated on applications of optics in sensor physics, in particular specializing in the use of ultrashort optical pulses for generating and detecting picosecond acoustic phonon pulses in thin films and multilayers. He developed a related phonon pulse detection technique based on the measurement of picosecond surface motion. With this technique he demonstrated how ultrafast electron diffusion could be probed in metals, and he contributed to the development of a theory of this diffusion, establishing an analytical relationship between the electron energy relaxation time and the electron-phonon and electron-electron coupling strengths.
Focusing in 2001-2002 at Hokkaido University on semiconductors, he measured the shape of picosecond acoustic phonon pulses generated in gallium arsenide, and was involved in similar spectroscopic experiments on semiconductor quantum wells.
In 2002 he also helped establish a method for watching ripples on crystals using ultrafast interferometry as well as making contributions to the theory of the detection of phonon pulses in multilayers.
He has also worked on the development of ultrasonic force microscopy and new local probe imaging techniques based on thermal waves at high frequencies and on nanometre length scales.
From 2004 he was involved in extending picosecond ultrasonics to shear waves, to liquids, and to contact mechanics, as well as spending time watching ripples travelling on phononic crystals and resonators.
More recently he has worked on gigahertz vibrations of nanostructures, including plasmonic crystals, and begun work on acoustic metamaterials.
Experiments and simulations on both optical and acoustic metamaterials interacting with GHz vibrations are presented. We firstly consider the extraordinary transmission of GHz surface acoustic waves through nanoscale metamaterial structures based on thin resonant bridges, showing how significant improvements in the acoustic transmission can be obtained at specific resonant frequencies. We then present the GHz modulation of the optical extraordinary transmission through a nanoscale hole-array structure, and the GHz modulation of the optical reflection from a split-ring resonator metamaterial that vibrates like an array of tiny tuning forks. Possible applications of this work are in ultrafast modulation and sensing.
Controlling sound or light is essential to a diverse range of applications. Periodic and aperiodic acoustic structures formed of individual acoustic or electromagnetic resonators, under conditions in which the acoustic or optical wavelength is much smaller than the resonator spacing, provide a versatile way to block, absorb, guide or transmit sound or light. Understanding their behaviour has been the focus of much research. Such structures, known as metamaterials, can be constructed from meter to nanometer length scales. We show how, for micron-scale to nanoscale structures, they can be probed using ultrafast optics to generate gigahertz sound fields inside them and be used to modulate optical transmission, or achieve enhanced acoustic transmission. Prospects for applications of GHz acoustic waves in acoustic or optical metamaterials will also be presented.
Bio:
O. B. Wright initially specialized in low temperature solid state physics. During his PhD course he published a detailed account of the thermoelastic effect in glasses at low temperatures—a modern version of a rubber band experiment in which the temperature change of the band is monitored on stretching.
After obtaining an industrial post he concentrated on applications of optics in sensor physics, in particular specializing in the use of ultrashort optical pulses for generating and detecting picosecond acoustic phonon pulses in thin films and multilayers. He developed a related phonon pulse detection technique based on the measurement of picosecond surface motion. With this technique he demonstrated how ultrafast electron diffusion could be probed in metals, and he contributed to the development of a theory of this diffusion, establishing an analytical relationship between the electron energy relaxation time and the electron-phonon and electron-electron coupling strengths.
Focusing in 2001-2002 at Hokkaido University on semiconductors, he measured the shape of picosecond acoustic phonon pulses generated in gallium arsenide, and was involved in similar spectroscopic experiments on semiconductor quantum wells.
In 2002 he also helped establish a method for watching ripples on crystals using ultrafast interferometry as well as making contributions to the theory of the detection of phonon pulses in multilayers.
He has also worked on the development of ultrasonic force microscopy and new local probe imaging techniques based on thermal waves at high frequencies and on nanometre length scales.
From 2004 he was involved in extending picosecond ultrasonics to shear waves, to liquids, and to contact mechanics, as well as spending time watching ripples travelling on phononic crystals and resonators.
More recently he has worked on gigahertz vibrations of nanostructures, including plasmonic crystals, and begun work on acoustic metamaterials.
Links
Practical information
- General public
- Free
Organizer
- The Institute of Microengineering (IMT) and the Lausanne Centre for Ultrafast Science (LACUS)
Contact
- Schafer Isabelle <[email protected]>