In general relativity, a gravitational white hole is a hypothetical region of space that cannot be entered from outside. It is the reverse of a black hole from which light and information cannot escape. Researchers from the University of Southampton, Nanyang Technological University and Texas A&M University have created an optical device exhibiting intriguing similarities to these objects. The device will either totally absorb (optical black hole) or totally reject (optical white hole) light of any wavelength, depending on its polarization.
Double-prism device with thin film in between shown as dark light absorbing plane — mimicking a gravitational black hole. Image credit: Nina Vaidya, University of Southampton.
The newly-developed device functions as an optical black hole or optical white hole, and rests on a principle known as coherent perfect absorption of light waves.
Dependent on polarization, this optical device can either absorb or reject light almost entirely, analogous to the behavior of a gravitational black or white hole in space.
The device works by forming a standing wave from incident light waves, where interactions with an ultrathin absorber lead to perfect absorption or transmission, based on the polarization of the light.
In simple terms, it behaves like a cosmic object that either swallows or repels light.
“Celestial phenomena, especially black holes, have fascinated the imagination and exploratory intrigue of humans for generations,” said University of Southampton’s Professor Nina Vaidya.
“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.”
The team’s proof-of-concept experiments demonstrate that this optical device manipulates electromagnetic waves in a way that mirrors the behavior of gravitational black and white holes.
Simulations illustrate the absence of reflection from the device for the black hole analog and the formation of a standing wave due to interference of incident and reflected light for the white hole.
The results illuminate fascinating insights and possibilities of manipulating light-matter interactions and may enable wide-ranging practical applications.
“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,” Professor Vaidya said.
The team’s work was published in the journal Advanced Photonics.
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Eric Plum et al. 2025. Optical analog of black and white gravitational holes. Advanced Photonics 7 (2): 025001; doi: 10.1117/1.AP.7.2.025001
