Control of sound waves through Klein tunnels improves filtering of acoustic signals

In the context of sensory modalities, the eyes function like tiny antennas, picking up light and electromagnetic waves traveling at great speed. When humans look at the world, their eyes capture these waves and convert them into signals that the brain reads as color, shape, and movement. This is a seamless process and allows people to see details clearly even when there is a lot going on around them.

The ear, on the other hand, acts like a microphone, capturing sound through air vibrations. When someone speaks, sound waves hit your eardrum, causing it to vibrate and send signals to your brain. But unlike the clarity the eyes provide, the ears can struggle in noisy environments where different types of sounds overlap.

Dr. Yue Jiang, a student in the Charlie Johnson Group at the University of Pennsylvania, compares this challenge to what scientists face when trying to filter sound with modern technology. “Especially now that wireless communication has become essential, we need a way to separate important signals from noise,” Jiang says. “With countless signals being transmitted from different directions, it is easy for interference to disrupt the transmission.”

To achieve this goal, Jiang and her team at the Johnson Group developed a method to control sound waves using a process called Klein tunneling, which applies to high frequency ranges.

“What’s interesting about this is that it pushes Klein tunneling, the movement of particles like electrons through energy barriers, into the gigahertz range,” says Charlie Johnson. “These are the frequencies your mobile phone operates on, so our findings could lead to faster and more reliable communication systems.”

The team’s research, published in the journal Device, is the first to demonstrate Klein tunneling using sound waves at such a high frequency, paving the way for more efficient, faster and noise-tolerant communication systems and for quantum information systems. influence Precise control of sound is important. By fine-tuning the way sound waves travel, this research could lead to more reliable wireless communications and advanced technologies.

At the core of their research are phononic crystals, artificial materials designed to manipulate sound waves in a similar way that photonic crystals control light. The researchers etched a “snowflake-like” pattern into an ultra-thin film made of aluminum nitride, a piezoelectric material that converts electrical signals into mechanical waves and vice versa. These patterns play an important role in guiding sound waves to Dirac points. Crosses energy barriers with minimal energy loss.

The membrane is just 800 nanometers thick and was designed and manufactured at Penn State’s Shin Nanotechnology Center.

“Snowflake patterns allow us to fine-tune the way waves pass through the material, which can reduce unwanted reflections and increase signal clarity,” Jiang says.

To confirm their results, the researchers collaborated with Keji Rai’s research group at the University of Texas at Austin and used transmission mode microwave impedance microscopy (TMIM) to visualize the sound waves in real time. “TMIM allows us to observe these waves traveling through the crystal at gigahertz frequencies, giving us the precision we need to confirm that Klein tunneling is occurring,” says Jiang. says Mr.

The team’s success builds on previous work with Lai’s lab that investigated the control of sound waves at low frequencies. “Previous work with Keji helped us understand wave manipulation,” Johnson says. “The challenge was to extend that understanding to even higher frequencies.”

In recent experiments, the team demonstrated near-perfect transmission of sound waves at frequencies between 0.98 GHz and 1.06 GHz. By controlling the angle at which the waves enter the phononic crystal, they can be guided into the barrier with little energy loss, making the method a highly effective method for filtering and directing audio signals.

As team members move forward, they are exploring the potential applications of their findings in areas such as 6G wireless communications, where the demand for faster data transmission and less interference is critical.

“More precise control of sound waves allows more users to connect simultaneously in densely populated frequency bands,” Jiang says.

They are also testing new materials, such as scandium-doped aluminum nitride, which could enhance the Klein tunneling effect and give even better performance at higher frequencies. “We are pushing the envelope to see how far we can extend these principles and how they can be applied to both classical and quantum technologies,” says Zhang. .

The researchers ultimately hope to develop ultra-high-precision, angle-dependent filters for a variety of applications, including wireless communications, medical imaging, and quantum computing.

“This study is just the beginning,” Johnson said. “We are poised for a new generation of acoustic devices that could revolutionize the way we think about the transmission and control of sound waves.”