The team based their design on the concept of coherent perfect absorption, enabling the device to either fully absorb or repel light, depending on the polarization. This dual functionality mirrors the opposing characteristics of black holes, which trap all incoming light and matter, and white holes, which are theorized to emit energy and resist all incoming matter.

The mechanism involves the formation of a standing wave between incident light beams, which interacts with an ultrathin absorber to create near-total absorption or reflection. This outcome hinges on the polarization of the incoming light, making the device's behavior tunable and directionally specific.

"Celestial phenomena, especially black holes, have fascinated the imagination and exploratory intrigue of humans for generations," explained senior corresponding author Nina Vaidya, professor at the University of Southampton. "Analogs are ways of accessing physics, especially for far away objects like the black holes, as the mathematical frameworks and aspects of the physical principles repeat themselves in surprising ways in several systems-celestial phenomenon to nano- and pico-scale devices. We introduce the concept of optical black and white holes that deterministically absorb almost all light of one polarization while rejecting light of the orthogonal polarization. It relies on our experimental demonstration of broadband coherent perfect absorption in compact devices, enabled by spatial coherence and interference, while polarization sensitivity is acquired from the geometrical phase of the interfering beams."

Simulations and laboratory demonstrations confirmed that the device successfully emulates the characteristics of gravitational black and white holes. For black hole analogs, no reflected light was detected, while the white hole configuration produced standing waves from the interplay of incident and reflected beams.

Beyond its conceptual significance, the optical analog has potential applications across diverse domains, including detection systems, energy harvesting, spectral camouflage, and stealth technology. "Our optical device can be employed as an analog to study and explore the physics of these far away celestial phenomena; or indeed to provide a practical framework for several potential applications of tailoring of electromagnetic waves and enhanced light-matter interactions, such as detection, energy conversion, multispectral camouflage, stealth technologies, and more," added Vaidya.

Research Report:Optical analog of black and white gravitational holes

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University of Southampton
Understanding Time and Space