How to Trap a Mechanical Wave and Store Its Energy

Researchers at the Advanced Science Research Center at The Graduate Center, CUNY, have found a way to play a “trick” on mechanical waves. Their method lets the scientists store the waves indefinitely without losing energy, and release them on demand in a specific direction.

The research could lead to advances in quantum computing and ultra-low energy photonics, the authors say. As mechanical waves are used to evaluate the integrity of bridges, the study could also contribute to improvements in testing technology.

Authors on the study, published in Science Advances, include Younes Ra’di, a CUNY ASRC Photonics research professor, and Andrea Alù, the founding director of the Photonics Initiative at the CUNY ASRC.

If you wanted to store a light wave, you could build a box of mirrors and trap it inside. But this box won’t be perfect—some of your photons, or particles of light, will inevitably leak out. The same is true for mechanical waves, like the vibration of a guitar string: Storage tends to be inefficient.

The team has experimentally demonstrated a way around this. Their setup used an aluminum rod with vibrating elements at either end to create waves, and a resonator in the middle. When the waves hit the resonator, some of their energy wants to reflect or scatter away. By changing the strength of the vibrations, the researchers can control how the waves evolve over time and are thus able to cancel out any attempted escapes.

This way the waves are effectively stored in the resonator. Detuning the vibrations or stopping them altogether then releases the waves.

“We are currently exploring the application of similar concepts to other types of waves, including light,” Alù said in an interview with Newsweek. “We envision efficient devices for optical computing and quantum computing based on similar principles, and improving the efficiency of wireless charging, memories and switches.”