Marshall University Physics Professor Dr. Thomas E. Wilson’s research on high-frequency acoustics has resulted in the discovery of the acoustic equivalent of a laser, and will be reported as a Rapid Communication in Physical Review B, a leading scientific publication.

Compared to optical lasers, the development of acoustic lasers is in its infancy. Wilson’s approach stems from a so-called “non-linear” light/sound interaction that can occur in a custom atomic-layered “superlattice.” To Wilson’s knowledge, there are only two other instances of acoustic lasers that have been developed.

Wilson’s approach is advantageous because there are no electronic transitions involved, which would create waste heat. Also, the fabrication of Wilson’s acoustic parametric oscillator is simpler because it does not use conventional mirrors, as most lasers require.

The research describes his approach to creating a source of coherent acoustic waves, equivalent to an acoustic laser, and one that operates at record-high frequencies in which the acoustic wave quanta are called “phonons.” This equivalent to an acoustic laser is a “self-starting mirrorless acoustic parametric oscillator based upon a nonlinear acousto-optic degenerate four-wave mixing” that he developed. Researchers have been pursuing an acoustic laser for decades.

“Wave phenomena are ubiquitous in musical acoustics and hospital ultrasounds, and the same effect occurs in my device, except at much higher frequencies,” Wilson said. “In this process, there is an effective, acoustic mirror that appears spontaneously, a ‘phase-conjugate’ mirror, during the four-wave mixing. That means I don’t have to fabricate mirrors, which is a complicated process.”

Light lasers have been used in everything from retail scanners to CD players to surgery, so the potential for the acoustic laser could be broad as well. Such lasers could be used in ultrasounds to safely increase beam quality. Using a parametric oscillator to extend ultrasonic imaging into the nanoscale is one exciting prospect, he said.

“This research has been a long, fascinating journey. Phonon physics has been my life’s work,” Wilson said, adding that his first funding came during President Reagan’s administration and resulted in his invention of a “cavity-dumped” far-infrared laser. “This recent and totally unexpected discovery of the acoustic parametric oscillator is icing on the cake.”

He has been invited to present his research at the Fourth International Conference on Metamaterials and Nanophotonics in July 2019 in St. Petersburg, Russia. Wilson will speak during a special session on phonons. He is also organizing the 16th International Conference on Phonon Scattering in Condensed Matter – PHONONS 2021, to be held at Marshall University in 2021.

“Thomas has emerged as a leader in the field of acoustic lasers, which is a wonderful thing for the College of Science, and for our students,” said Dr. Chuck Somerville, dean of the Marshall University College of Science. “He has clearly demonstrated the importance of determination and persistence, and it is great to know that his work is now gathering international interest.”

Originally from Jean Hardiman for Marshall University Communications