Acoustic Saser Laser Realized

A new type of acoustic laser device called a ‘Saser’ has been realized by a curious group of scientists at the University of Nottingham. In collaboration with colleagues in the Ukraine, the group has produced the sonic equivalent to the laser and it produces an intense beam of uniform sound waves (rather than light waves) on the nanoscale.

According to group, the new device could have significant and useful applications in the worlds of computing, imaging, and even anti-terrorist security screening.

Where a laser uses packets of electromagnetic vibrations called photons, the Saser uses sound waves composed of sonic vibrations called phonons. In a laser, the photon beam is produced by stimulating electrons with an external power source so they release energy when they collide with other photons in a highly reflective optical cavity. This produces a coherent and controllable shining beam of laser light in which all the photons have the same frequency and rate of oscillation. From supermarket scanners to DVD players, surgery, manufacturing and the defense industry, the application of laser technology is widespread.

The Saser mimics this technology but using sound, to produce a sonic beam of phonons which travels, not through an optical cavity like a laser, but through a tiny manmade structure called a superlattice. This is made out of roughly 50 super-thin sheets of two alternating semiconductor materials, Gallium Arsenide and Aluminium Arsenide, each layer just a few atoms thick. When stimulated by a power source (a light beam), the phonons multiply, bouncing back and forth between the layers of the lattice, until they escape out of the structure in the form of an ultra-high frequency phonon beam.

A key factor in this new science is that the Saser is the first device to emit sound waves in the terahertz frequency range – the beam of coherent acoustic waves it produces has nanometer wavelengths. Crucially, the superlattice device can be used to generate, manipulate and detect these sound waves making the Saser capable of widespread scientific and technological applications.

One example of its potential is as a sonogram, to look for defects in nanometer scale objects like micro-electric circuits. Another idea is to convert the Saser beam to THz electromagnetic waves, which may be used for medical imaging and security screening. High intensity sound waves can also change the electronic properties of nanostructures so a Saser could be used as a high-speed terahertz clock to make the computers of the future a thousand times faster.

“While our work on sasers is driven mostly by pure scientific curiosity, we feel that the technology has the potential to transform the area of acoustics, much as the laser has transformed optics in the 50 years since its invention,” said Anthony Kent, professor at the University of Nottingham’s School of Physics and Astronomy.

The research team at Nottingham, with help from Borys Glavin of the Lashkarev Institute of Semiconductor Physics in the Ukraine, has won the immediate accolade of the publication of their paper on the Saser experiments in this month's journal, Physical Review. The team has also won a grant from the Engineering and Physical Sciences Research Council to develop Saser technology over the next four years.

For more information, visit: www.nottingham.ac.uk