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 New proton record: Researchers measure magnetic moment with greatest possible precision
24.11.2017 | Johannes Gutenberg-Universität Mainz

nachricht Enhancing the quantum sensing capabilities of diamond
23.11.2017 | The Hebrew University of Jerusalem

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: New proton record: Researchers measure magnetic moment with greatest possible precision

High-precision measurement of the g-factor eleven times more precise than before / Results indicate a strong similarity between protons and antiprotons

The magnetic moment of an individual proton is inconceivably small, but can still be quantified. The basis for undertaking this measurement was laid over ten...

Im Focus: Frictional Heat Powers Hydrothermal Activity on Enceladus

Computer simulation shows how the icy moon heats water in a porous rock core

Heat from the friction of rocks caused by tidal forces could be the “engine” for the hydrothermal activity on Saturn's moon Enceladus. This presupposes that...

Im Focus: Nanoparticles help with malaria diagnosis – new rapid test in development

The WHO reports an estimated 429,000 malaria deaths each year. The disease mostly affects tropical and subtropical regions and in particular the African continent. The Fraunhofer Institute for Silicate Research ISC teamed up with the Fraunhofer Institute for Molecular Biology and Applied Ecology IME and the Institute of Tropical Medicine at the University of Tübingen for a new test method to detect malaria parasites in blood. The idea of the research project “NanoFRET” is to develop a highly sensitive and reliable rapid diagnostic test so that patient treatment can begin as early as possible.

Malaria is caused by parasites transmitted by mosquito bite. The most dangerous form of malaria is malaria tropica. Left untreated, it is fatal in most cases....

Im Focus: A “cosmic snake” reveals the structure of remote galaxies

The formation of stars in distant galaxies is still largely unexplored. For the first time, astron-omers at the University of Geneva have now been able to closely observe a star system six billion light-years away. In doing so, they are confirming earlier simulations made by the University of Zurich. One special effect is made possible by the multiple reflections of images that run through the cosmos like a snake.

Today, astronomers have a pretty accurate idea of how stars were formed in the recent cosmic past. But do these laws also apply to older galaxies? For around a...

Im Focus: Visual intelligence is not the same as IQ

Just because someone is smart and well-motivated doesn't mean he or she can learn the visual skills needed to excel at tasks like matching fingerprints, interpreting medical X-rays, keeping track of aircraft on radar displays or forensic face matching.

That is the implication of a new study which shows for the first time that there is a broad range of differences in people's visual ability and that these...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Ecology Across Borders: International conference brings together 1,500 ecologists

15.11.2017 | Event News

Road into laboratory: Users discuss biaxial fatigue-testing for car and truck wheel

15.11.2017 | Event News

#Berlin5GWeek: The right network for Industry 4.0

30.10.2017 | Event News

 
Latest News

Lightning, with a chance of antimatter

24.11.2017 | Earth Sciences

A huge hydrogen generator at the Earth's core-mantle boundary

24.11.2017 | Earth Sciences

Scientists find why CP El Niño is harder to predict than EP El Niño

24.11.2017 | Earth Sciences

VideoLinks
B2B-VideoLinks
More VideoLinks >>>