( Phonon Laser )
American Institute of Physics
Physics News ( Number 779 ); June 2, 2006
A New Kind of Acoustic Laser
Sound amplification by stimulated emission of radiation, or SASER, is the acoustic analog of a laser. Instead of a feedback-built potent wave of electromagnetic radiation, a saser would deliver a potent ultrasound wave.
The concept has been around for years and several labs have implemented models with differing features. In a new version, undertaken by scientists from the University of Nottingham (Anthony Kent, email@example.com) in the U.K. and the Lashkarev Institute of Semiconductor Physics in Ukraine, the gain medium -- that is, the medium where the amplification takes place -- consists of stacks (or a superlattice) of thin layers of semiconductors which together form "quantum wells."
In these wells, really just carefully confined planar regions, electrons can be excited by parcels of ultrasound, which typically possess millielectronvolts of energy, equivalent to a frequency of 0.1-1 terahertz. And just as coherent light can build up in a laser by the concerted, stimulated emission of light from a lot of atoms, so in a saser coherent sound can build up by the concerted emission of phonons from a lot of quantum wells in the superlattice.
In lasers the light buildup is maintained by a reflective optical cavity. In the U.K.-Ukraine saser, the acoustic buildup is maintained by an artful spacing of the lattice layer thicknesses in such a way that the layers act as an acoustic mirror.
Eventually the sound wave emerges from the device at a narrow angular range, as do laser pulses. The monoenergetic nature of the acoustic emission, however, has not yet been fully probed. The researchers believe their saser is the first to reach the terahertz frequency range while using also modest electrical power input. Terahertz coherent sound is itself a relatively new field of research. Essentially ultrasound with wavelengths measured in nanometers, terahertz acoustical devices might be used in modulating light waves in optoelectronic devices.
Kent et al., Physical Review Letter, 2 June 2006
Contact : Anthony Kent, firstname.lastname@example.org
A schematic illustrating how the acoustic analog of a laser works. The top image shows the structure of a superlattice of semiconductor layers and confined acoustic waves undergoing amplification. The bottom image shows the energy levels of electrons confined in the superlattice layers; one phonon in can produce two phonons coming out.
SASER DIODE DRIVING CIRCUIT
Inventor(s): NAGANO GAZHI [JP]
Applicant(s): TOKYO SHIBAURA ELECTRIC CO [JP]
Classification: - international: H01S3/00; H01S3/00; (IPC1-7): H01S3/00
Nonlinear Saser with Multiple Pumps
CAHILL MARK DAVID
Classification: - international: G10K15/04; G10K15/04; (IPC1-7): G10K15/04; H04R23/00- European: G10K15/04
Abstract -- The amplification, detection or generation of a sound 3 by causing it to form a standing wave, a sasing mode, and causing this standing wave to interact with other standing waves, pump modes, 1 of sound. At least one of the pump modes has a frequency close to that of the sound to be amplified, detected or generated, and another one has a different frequency, the amplitudes of these other standing waves varying in time or space.
Inventor(s): CAHILL MARK DAVID
Classification: - international: G10K15/04; G10K15/04; (IPC1-7): G10K11/08; H04R23/00 - European: G10K15/04
Abstract -- A sound wave of a particular frequency and travelling in a particular direction is amplified by causing it to interact with a high-amplitude standing wave of the same frequency, but oscillating in a different direction to the sound wave. The standing wave (pump mode) is set up in a suitable medium, e.g. a liquid alcohol such as ethanol, between acoustic mirrors 1. The sound wave to be amplified (sasing mode) enters the medium through partly-transparent mirrors 2.
A SASER operates on principles remarkably similar to those of a laser. A stack of thin semiconductor wafers are placed in a lattice within an acoustically reflective chamber. Upon the addition of electrons, short-wavelength (in the terahertz range) phonons are produced. Since the electrons are confined to the quantum wells existing within the lattice, the transmission of their energy depends upon the phonons they generate. As these phonons strike other layers in the lattice, they excite electrons, which produce further phonons, which go on to excite more electrons, and so on. Eventually, a very narrow beam of high-frequency ultrasound exits the device.
Apart from allowing the investigation of terahertz-frequency ultrasound, the SASER is also likely to find a myriad of uses in optoelectronics, as a method of signal modulation and/or transmission. 
A theoretical scheme of a saser (Sound Amplification by Stimulated Emission of Radiation) is proposed. A liquid with gas bubbles is used as the active medium. Pumping is performed with an alternating electric field or mechanical vibrations of the resonator. Phase bunching of initially incoherent radiators (bubbles) occurs under the action of acoustic radiation forces. The proposed scheme is similar to that of a free-electron laser. Two models of an active medium are studied. In the first model it is assumed that all bubbles have the same radius. In the second model a continuous distribution of bubble radii is studied. The starting values for sasers with square and cylindrical resonators are calculated. It is shown that in all cases studied these conditions are identical, to within a numerical factor. The operation of a saser in a nonlinear regime and the directional pattern of a saser in the saturation regime are studied.
reply to post by Merkeva
Use your imagination. You can make somebody miles away hear, what you want to say. And probably only he hears the sound "in his head" and nobody else near him.
And you could brake walls, resonating at the right spots with a right rythm/amplitude(/wave shape) - from a distance. It can be also very harmful to the people.
And maybe with that principle you can transmit some quantity of energy through the air. Ad more: think of leaver and ultrasonic technology. If they can break stones inside the soft tissue, maybe they could cause changes on a microlevels of matter being. Let's say melt a metal without heating it then mixed it with some liquid. And break stone or ice in the mountains, on a safe distance. Clean work, cheap too. Very harmful.
And the new era of discoteques... where each wisitor would hear different music, according to his coordinates/position in the room. The name could be Music on the spot or something.
Anyway, there's an interesting stuff on a google video named Cymatics soundscape. There you can see, what soud does to matter.
Or better, you see a dance of creative sound and willing matter.
Shock Amplification by System with Energy Release (SASER)
V. Kedrinskii, Yu. Shokin, V. Vshivkov, G. Dudnikova
Lavrentyev Institute of Hydrodynamics, Institute of Computational Technology, Novosibirsk 630090, Russia
The paper is devoted to one of approaches to the solution of so-called problem of ``Acoustical Laser'' (acoustical analogy of laser system). In this connection primary attention is focused on the heterogeneous structure of reactive liquids containing macroinhomoheneities which can be a main reason of arising such known phenomena as bubbly detonation and explosion of a combustible liquids stored under pressure in containers when they are suddenly depressurized.
One can mention about some analogies of LASER/SASER systems : 1. adiabatic explosion of gas mixture into the bubbles (hot-spot system formation) of reactive bubbly system can be considered as a physical analogy of pumping process of laser system; 2. an energy release during the process of wave propagation above the hot-spot system and its amplification is an analogy of ``forced radiation'' effect. Statement features of numerical study presented consist in that a wave process development both in passive and reactive bubbly systems as a set of layers is considered when boundary as well as physical conditions can be changed for the certain instants of time according to the given program. In particular the model allows a reactive gas mixture to be reconstracted after an igniting detonation behind the wave passed. The calculations have shown that in such kind systems a pressure can be ``pumped'' up to a rather high level.
Electrically pumped terahertz SASER device using a weakly coupled AlAs/GaAs superlattice as the gain medium
R. N. Kini *, N. M. Stanton, A. J. Kent, M. Henini
School of Physics and Astronomy, University of Nottingham, University Park, Nottingham, NG7 2RD UK
email: R. N. Kini (email@example.com)
*Correspondence to R. N. Kini, School of Physics and Astronomy, University of Nottingham, University Park, Nottingham, NG7 2RD UK
Abstract -- We describe an electrically pumped sound amplification by stimulated emission of radiation (SASER) device for terahertz frequencies. The gain medium of the device is a weakly coupled AlAs/GaAs superlattice (SL). It is incorporated into a multimode acoustic cavity formed between the top (free) surface of the structure and a second SL acting as a phonon reflector. We report measurements on a prototype device using bolometers to detect the emitted phonons. An enhancement of the phonon emission parallel to the SL growth direction is observed when the energy drop per period of the gain SL matched the cavity phonon energy. This was accompanied by a small increase in device current. We argue that these results provide evidence that the device is operating as a SASER. (© 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)
Ultrasonics Symposium, 1999. Proceedings. 1999 IEEE ; Volume 1, Issue , 1999 Page(s):509 - 511 vol.1
Principles of a Mechanical Type Saser
Leach, M.F.; Goldsack, D.E.; Kilkenny, C.
Summary: Musical sands, as well as common materials such as silica gel, emit inordinately intense audible sounds when sheared by wind, waves or other mechanical means. Hand shaken laboratory size samples of these materials produce very coherent beat-like signals, when displayed on an oscilloscope. Frequency parameters of these patterns have been related to particle size, and, more surprisingly perhaps, to sand sample size. By combining these two relationships, a simple method for creating a source of single frequency sound has been developed. It consists of filtering musical sands into narrow size fractions and then tailoring an appropriate size distribution which can be finely tuned to any given frequency within the frequency range defined by the whole sample. Thus, the principles for developing an active device that converts input mechanical energy into a narrow intense beam of coherent audible sound have been established
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