Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Amplification of Sound Waves at Extreme Frequencies

22.02.2016

An electric current through a semiconductor nanostructure amplifies sound waves at ultrahigh frequency. This method allows for novel, highly compact sources of ultrasound, which can serve as diagnostic tool for imaging materials and biological structures with very high spatial resolution.

Ultrasound is an acoustic wave at a frequency well above the human audible limit. Ultrasound in the megahertz range (1 MHz = 106 Hz = 1 million oscillations per second) finds broad application in sonography for, e.g., medical imaging of organs in a body and nondestructive testing of materials. The spatial resolution of the image is set by the ultrasound wavelength.


Changes of the sample reflectivity as a function of the delay time after the pump pulse. The observed oscillations are proportional to the instantaneous amplitude of the sound wave. The blue curve shows the results without the current through the superlattice, the red curve with a current of 1 A. With current the amplitude is always larger than without current. The amplification (the ratio between the red and blue curves) is most pronounced at delay times of 300 ps (1 picosecond (ps) is 10-12 s, one millionth of a millionth of a second), since the amplification takes time. Fig.: MBI

To image objects on the nanoscale (1 nanometer = 10to the-9 m = 1 billionth of a meter), sound waves with a frequency of several hundreds of gigahertz (1 gigahertz (GHz) = 1000 MHz) are required. To develop such waves into a diagnostic tool, novel sources and sound amplification schemes need to provide sufficient sound intensities.

In a recent publication (K. Shinokita et al., Phys. Rev. Lett. 116, 075504 (2016)), researchers from the Max-Born-Institut in Berlin together with colleagues from the Paul-Drude-Institut, Berlin, and the École Normale Supérieure, Paris, have demonstrated a new method for sound amplification in a specially designed semiconductor structure consisting of a sequence of nanolayers. Sound waves with a frequency of 400 GHz are generated and detected with short optical pulses from a laser.

The sound is amplified by interaction with an electric current traveling through the semiconductor in the same direction as the sound waves. The sound amplification is based on a process called "SASER", the Sound Amplification by Stimulated Emission of Radiation, in full analogy to the amplification of light in a laser.

The sound wave stimulates electrons moving with a velocity higher than the sound velocity, to go from a state of high energy to a state of lower energy and, thus, make the sound wave stronger. To achieve a net amplification, it is necessary that there are more electrons in the high-energy than in the lower-energy state. In this way, a 400 GHz sound wave is amplified by a factor of two.

The present work is a proof of principle. For a usable source of high-frequency sound waves, it is necessary to further increase the amplification, which should be possible by improving the design of the structure and, most importantly, better cooling of the semiconductor device. Once such a source is available, it can be used for extending the spatial resolution of sonography towards the scale viruses, a length scale much shorter than the wavelength of visible light.


Original Publication: Physical Review Letters 116, 075504
Strong Amplification of Coherent Acoustic Phonons by Intraminiband Currents in a Semiconductor Superlattice

Keisuke Shinokita, Klaus Reimann, Michael Woerner, Thomas Elsaesser, Rudolf Hey, Christos Flytzanis

Contact
Prof. Klaus Reimann Tel. 030 6392 1476
Dr. Michael Wörner Tel. 030 6392 1470
Prof. Dr. Thomas Elsässer Tel. 030 6392 1400

This article was chosen as an Editor's suggestion, see also: Pumping up the sound

Weitere Informationen:

http://physics.aps.org/synopsis-for/10.1103/PhysRevLett.116.075504

Saskia Donath | Forschungsverbund Berlin e.V.

More articles from Physics and Astronomy:

nachricht Pulses of electrons manipulate nanomagnets and store information
21.07.2017 | American Institute of Physics

nachricht Vortex photons from electrons in circular motion
21.07.2017 | National Institutes of Natural Sciences

All articles from Physics and Astronomy >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Manipulating Electron Spins Without Loss of Information

Physicists have developed a new technique that uses electrical voltages to control the electron spin on a chip. The newly-developed method provides protection from spin decay, meaning that the contained information can be maintained and transmitted over comparatively large distances, as has been demonstrated by a team from the University of Basel’s Department of Physics and the Swiss Nanoscience Institute. The results have been published in Physical Review X.

For several years, researchers have been trying to use the spin of an electron to store and transmit information. The spin of each electron is always coupled...

Im Focus: The proton precisely weighted

What is the mass of a proton? Scientists from Germany and Japan successfully did an important step towards the most exact knowledge of this fundamental constant. By means of precision measurements on a single proton, they could improve the precision by a factor of three and also correct the existing value.

To determine the mass of a single proton still more accurate – a group of physicists led by Klaus Blaum and Sven Sturm of the Max Planck Institute for Nuclear...

Im Focus: On the way to a biological alternative

A bacterial enzyme enables reactions that open up alternatives to key industrial chemical processes

The research team of Prof. Dr. Oliver Einsle at the University of Freiburg's Institute of Biochemistry has long been exploring the functioning of nitrogenase....

Im Focus: The 1 trillion tonne iceberg

Larsen C Ice Shelf rift finally breaks through

A one trillion tonne iceberg - one of the biggest ever recorded -- has calved away from the Larsen C Ice Shelf in Antarctica, after a rift in the ice,...

Im Focus: Laser-cooled ions contribute to better understanding of friction

Physics supports biology: Researchers from PTB have developed a model system to investigate friction phenomena with atomic precision

Friction: what you want from car brakes, otherwise rather a nuisance. In any case, it is useful to know as precisely as possible how friction phenomena arise –...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Closing the Sustainability Circle: Protection of Food with Biobased Materials

21.07.2017 | Event News

»We are bringing Additive Manufacturing to SMEs«

19.07.2017 | Event News

The technology with a feel for feelings

12.07.2017 | Event News

 
Latest News

NASA looks to solar eclipse to help understand Earth's energy system

21.07.2017 | Earth Sciences

Stanford researchers develop a new type of soft, growing robot

21.07.2017 | Power and Electrical Engineering

Vortex photons from electrons in circular motion

21.07.2017 | Physics and Astronomy

VideoLinks
B2B-VideoLinks
More VideoLinks >>>