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Researchers from the Advanced Science Research Center at the CUNY Graduate Center and Florida International University have published their findings in the journal Science, shedding light on the innovative concept of complex frequency excitations. This emerging methodology offers a new means to manipulate light, sound, and other wave phenomena, pushing beyond traditional limitations in wave control and opening up possibilities for advanced wave-based technologies.
In existing technological frameworks that rely on light and sound waves—such as mobile phones, microscopes, speakers, and headphones—the ability to control wave phenomena is constrained by the intrinsic properties of the materials employed. Traditionally, overcoming these limitations has necessitated the use of complex materials, increased energy inputs, or the design of more intricate devices. In contrast, the concept of complex frequency excitations suggests a novel approach that enhances wave control without changing the underlying materials. By designing excitations to oscillate at complex frequencies, researchers can simulate effects like energy gain and loss within the system, achieving remarkable outcomes such as perfect absorption, super-resolution imaging, surpassing passive limits in wave interactions, and accessing non-Hermitian responses without relying on energy-consuming active components.
“This approach revolutionizes our strategy for controlling waves,” commented Andrea Alù, the study’s principal investigator. Alù is a Distinguished Professor and the Einstein Professor of Physics at the CUNY Graduate Center, as well as the founding director of the CUNY ASRC Photonics Initiative. “Our capabilities are no longer confined by the materials we use but are now determined by our ability to design the right excitations to shape the responses of wave-based systems.”
A New Frontier in Wave Physics
The research team elaborates on how signal excitations, which exhibit amplitudes that grow or decrease exponentially over time, can interact with the natural resonances and anti-resonances of various systems under certain conditions. This interaction mimics the effects created by strategically distributing materials with gain or loss properties. Potential applications for this technology span dynamic control of light, signal absorption and amplification, directional wave transport, and improved control over quantum states.
Alù’s team has been at the forefront of this field, conducting pioneering experiments that demonstrate controllable energy storage, advanced imaging techniques, enhanced wireless power transfer, and even manipulation of waves beyond typical passive limits. The advancements achieved through improved wave control promise to enhance medical imaging resolution, boost the efficiency of wireless communication, and refine the manipulation of wave-based quantum states for significant applications in quantum sensing and computing.
“While the current implementations of complex frequency excitations have primarily focused on lower frequency domains, such as radio and acoustic waves, extending this technique to higher frequency ranges, including optical systems, poses certain challenges,” noted Seunghwi Kim, the study’s first author and a postdoctoral researcher at ASRC. “Our findings establish a foundational framework that could spur future discoveries, providing a pathway for researchers in various areas of wave physics to investigate the vast potential of complex frequency excitations.”
This collaborative study engaged experts from the CUNY ASRC Photonics Initiative alongside the Department of Electrical and Computer Engineering at Florida International University, indicating a fruitful partnership in exploring advanced wave phenomena.
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