Non-linear phonons shrink front end wireless filters
Researchers in the US have developed semiconductor–piezoelectric heterostructures that can integrate multiple front end filters in wireless systems.
The team at the University of Arizona Wyant College of Optical Sciences and Sandia National Laboratories combined lithium niobate and indium gallium arsenide on a silicon substrate that enabled phonons to interact with each other much more strongly than in any conventional material for the front end filters on a single chip.
This produced nonlinear phononic interactions that they say could revolutionize classical and quantum information processing at radio frequencies in much the same way that nonlinear photonic interactions have at optical frequencies.
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Using a semiconductor allows the conversion efficiency can be further enhanced by applying semiconductor bias fields that amplify the phonons. The theoretical model accurately predicts the three-wave mixing efficiencies and extrapolates these nonlinearities far beyond what is possible today phonons to smaller dimensions in waveguides and optimizing the semiconductor material properties.
“Most people would probably be surprised to hear that there are something like 30 filters inside their cell phone whose sole job it is to transform radio waves into sound waves and back,” said Matt Eichenfield, at the UArizona College of Optical Sciences and Sandia National Laboratories in Albuquerque, New Mexico.
The group is integrating all the components needed for radio frequency signal processors using acoustic wave technologies instead of transistor-based electronics on a single chip but in a way that’s compatible with standard microprocessor manufacturing.
“Now, you can point to every component in a diagram of a radiofrequency front-end processor and say, ‘Yeah, I can make all of these on one chip with acoustic waves,'” said Eichenfield. “We’re ready to move on to making the whole shebang in the acoustic domain.”
Having all the components needed to make a radio frequency front end on a single chip could shrink devices such as cell phones and other wireless communication gadgets by as much as a factor of a 100, says Eichenfield.
The researchers demonstrated that one beam of phonons can change the frequency of another beam and manipulate the phonons.
“Normally, phonons behave in a completely linear fashion, meaning they don’t interact with each other,” he said. “It’s a bit like shining one laser pointer beam through another; they just go through each other.”
“When we combined the materials in just the right way, we were able to experimentally access a new regime of phononic nonlinearity,” said Sandia engineer Lisa Hackett, the lead author on the paper. “This means we have a path forward to inventing high-performance tech for sending and receiving radio waves that’s smaller than has ever been possible.”
By adding the indium-gallium arsenide semiconductor, Eichenfield’s group created an environment in which the acoustic waves traveling through the material influence the distribution of electrical charges in the indium gallium arsenide semiconductor film, causing the acoustic waves to mix in specific ways that can be controlled, opening up the system to various applications.
“The effective nonlinearity you can generate with these materials is hundreds or even thousands of times larger than was possible before, which is crazy,” Eichenfield said. “If you could do the same for nonlinear optics, you would revolutionize the field.”
www.nature.com/articles/s41563-024-01882-4
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