In the enigmatic realm of astrophysics, black holes have long stood as one of the universe’s most captivating and mysterious phenomena. These regions of spacetime are known for their intense gravitational pull, so strong that nothing, not even light, can escape once it crosses the event horizon. This cosmic characteristic renders them invisible, yet profoundly influential in the fabric of space and time. Contrasting their dark nature, the conceptual sibling of black holes, known as white holes, has remained largely hypothetical. Unlike black holes that absorb, white holes are theorized to expel matter and light, acting almost like a cosmic fountain. The boundary between these extraordinary cosmic objects and their real-world counterparts has now begun to blur, thanks to an innovative optical device developed by an international team of physicists and engineers.
The newly designed device mimics the behavior of both black holes and white holes by manipulating light at the nanoscale. Published in the esteemed journal Advanced Photonics, the research showcases a compact optical apparatus that operates based on the principle of “coherent perfect absorption” (CPA). CPA is a phenomenon where incident light waves are tuned to interfere constructively or destructively in such a way that all incoming light energy is either absorbed or transmitted with near-perfect efficiency. Through meticulous engineering, the device can be switched between modes where it either completely absorbs light—analogous to the black hole’s light-trapping characteristic—or wholly rejects it, thereby emulating the white hole’s theoretical expulsive nature.
At the core of this optical marvel lies a cleverly designed double-prism structure separated by an ultrathin planar film that acts as a perfect absorber. The device’s operation hinges heavily on the polarization state of incident electromagnetic waves. When polarized in one direction, the light waves form a standing wave pattern that is completely absorbed by this thin film, achieving near-total light absorption reminiscent of a black hole ensnaring photons beyond escape. Conversely, when polarized orthogonally, the same device allows light to pass through with minimal absorption, effectively rebuffing the incoming energy as a white hole would hypothetically eject matter and radiation.
The device’s functionality owes much to the interplay between spatial coherence and interference, phenomena deeply rooted in wave optics. Spatial coherence ensures that the incoming light waves maintain a fixed phase relationship, a prerequisite for forming stable standing waves upon reflection. Interference patterns arising from the interaction of these coherent waves and the absorbing film’s optical properties ultimately dictate whether absorption or transmission dominates. Furthermore, the device exploits the geometric phase associated with polarization states, granting it the unique ability to differentiate and selectively manipulate light based on its polarization vector.
Professor Nina Vaidya of the University of Southampton, who served as the senior corresponding author of the study, elucidates the significance of these optical analogs in probing celestial phenomena. She emphasizes that while direct observation and experimentation with astrophysical black holes are inherently limited by distance and scale, such analogous nanoscale devices afford a controlled environment to study and visualize related physical principles. This transposition from cosmic to laboratory scales leverages mathematical frameworks borrowed from general relativity, inviting a novel experimental platform to interrogate complex light–matter interactions that otherwise elude conventional experiments.
The research team’s rigorous proof-of-concept experiments intricately demonstrated the device’s dual behavior. Utilizing state-of-the-art optical instrumentation, they observed the near-perfect absorption of light in one polarization channel, indicated by the absence of reflected or transmitted waves corresponding to the “black hole” mode. Likewise, the complementary “white hole” mode generated a standing wave between the incident and reflected light, confirming the robust transmission and reflective properties that mirror theoretical white hole dynamics. Numerical simulations reinforced these observations, illustrating how the device manipulates the phase and amplitude of electromagnetic waves in a polarization-dependent manner, thus cementing its function as an optical analog to gravitational phenomena.
Beyond the fundamental scientific allure, this device promises a multitude of practical applications with potentially transformative impact in photonics, telecommunications, and energy management. Its ability to selectively absorb or transmit specific polarizations could enhance the design of optical detectors, improve energy harvesting mechanisms, and refine stealth technologies through advanced light-matter control. The inherently broadband nature of the coherent perfect absorption phenomenon ensures these capabilities span a wide spectral range, increasing the device’s versatility across various optical systems.
The conceptual leap embodied in this work also opens avenues for advanced multispectral camouflage. By tailoring the absorption and reflection properties dynamically through polarization control, devices can adaptively manipulate their optical signatures, finding use in military and civilian stealth applications. Coupled with the ultrathin physical footprint of the absorber, such devices are amenable to integration into compact, on-chip photonic circuits, merging astrophysical theory with practical engineering in an unprecedented way.
A particularly exciting aspect lies in the exploration of electromagnetic wave tailoring via geometric phase engineering. By exploiting the phase characteristics of polarized light, this mechanism permits deterministic control over light propagation paths, fostering new paradigms in waveguide design, optical switching, and signal modulation. This precise control over coherence and interference could spur advances in quantum information processing where the manipulation of light’s phase and polarization states is crucial.
Moreover, by offering a tangible analogy to black and white holes, this development enriches educational and outreach endeavors, fostering a deeper public understanding of gravitational astrophysics through accessible optical experiments. Students and researchers can now visualize complex relativistic concepts within laboratory confines, bridging the gap between abstract theory and experimental physics in engaging and comprehensible forms.
This research stands as a testament to the fruitful cross-pollination between disparate fields—astrophysics most notably intertwining with condensed matter physics and applied optics. It exemplifies how concepts inspired by the vast cosmos can directly influence and inspire novel optoelectronic device architectures that address modern-day scientific and industrial challenges.
In conclusion, the creation of an optical structure that emulates black and white holes marks a profound stride forward in both fundamental science and applied technology. By harnessing coherent perfect absorption and polarization-dependent responses, researchers have crafted a device that not only embodies deep cosmic principles but also unlocks a host of opportunities across photonics and beyond. As this field continues to evolve, such innovative analogs will remain invaluable tools, demystifying the universe’s mysteries while propelling next-generation optical technologies.
Subject of Research: Optical analogs of black and white gravitational holes based on coherent perfect absorption of light.
Article Title: Optical analog of black and white gravitational holes
News Publication Date: 27-Feb-2025
Web References:
- https://www.spiedigitallibrary.org/journals/advanced-photonics/volume-7/issue-02/025001/Optical-analog-of-black-and-white-gravitational-holes/10.1117/1.AP.7.2.025001.full
- http://dx.doi.org/10.1117/1.AP.7.2.025001
References:
E. Plum et al., “Optical analog of black and white gravitational holes,” Adv. Photon., 7(2), 025001 (2025), doi: 10.1117/1.AP.7.2.025001.
Image Credits: Nina Vaidya (University of Southampton).
Keywords
Light matter interactions, Black holes, Electromagnetic waves, Optical devices, Light polarization, Electronic coherence, Experimentation, Theoretical physics, Gravitation, Staff scientists, Geometry, General relativity, White matter, Mathematical physics, Light beams, Research and development, Energy harvesting, Electromagnetic spectrum, Spacetime, Cosmic rays.
