Introduction
Creating invisibility usually comes with challenges, but a recent design by researchers at the University of California, San Diego, offers a promising solution. They developed a thin and lossless “carpet cloak” that scatters light, making an object appear as if it’s a flat surface. Unlike traditional cloaking devices, this design is approximately one-tenth the size of the wavelength of the scattered photons, making it more practical.
Instead of using metal, which absorbs light, the cloak employs two dielectric materials—a Teflon substrate with ceramic cylinders. The varying heights of these cylinders, designed by a computer pattern, alter the light’s phase, mimicking that of a flat surface. Despite these height differences, the cloak remains incredibly thin, resembling a two-dimensional metasurface. This innovative approach holds promise for more practical and efficient invisibility cloaks in certain applications. The research, led by Boubacar Kante, an assistant professor at UCSD, is detailed in the latest issue of Progress in Electromagnetics Research.
While this specific cloak currently resides in a computer simulation, the research team, led by Kante, is actively pursuing the creation of a physical version. Originally designed for the microwave range with a thickness of 0.6 cm to handle 6 cm wavelengths, the team chose larger dimensions for ease of construction. While a cloak for visible light would need to be much thinner (less than 40 nm), achievable through established photolithography processes, the microwave version holds potential military applications, effectively concealing objects from radar operating at those wavelengths.
However, a notable tradeoff exists—the narrow range of covered wavelengths. Expanding the design to encompass a broader spectrum compromises material efficiency.
Kante envisions potential applications beyond invisibility, such as shielding antennas in cell towers to minimize crosstalk or improving solar concentrators for more efficient sunlight concentration to power steam turbines.
How does invisible cloth work?
Using transformation optics, space is bent away from a planar surface, leaving a gap underneath within which objects may be hidden. Light waves incident upon the carpet cloak are reflected as if from the planar surface below.
Unlike the PSSC, this device can be constructed with nearly isotropic materials; furthermore, it does not require infinite phase velocities and therefore can be constructed to work over a larger frequency range. These simplifications have resulted in a number of experimental realizations, which will be discussed in the next section. However, it has been shown by Zhang, Chan, and Wu (2010) that a carpet cloak designed without any anisotropy results in a lateral shift of the reflected wave that in principle makes the cloaked region detectable.
How do you explain invisibility?
Invisibility is the state of an object that cannot be seen. An object in this state is said to be invisible (literally, “not visible”). The phenomenon is studied by physics and perceptual psychology.
The natural perception of objects stems from the visible spectrum of light reflecting off surfaces and reaching the observer’s eye. In the context of invisibility, the most intuitive concept involves an object that neither reflects nor absorbs light, allowing it to transmit light through—this quality is termed transparency. Many materials in nature exhibit varying degrees of transparency, although true 100% transparency is not naturally occurring.
The perception of invisibility is influenced by optical and visual factors, with variations based on the observer’s eyes or the instruments employed. An object may be deemed “invisible to” a person, animal, or instrument, and research indicates that the perception of invisibility occurs cyclically in sensorial studies.
Invisibility is often regarded as the ultimate form of camouflage because it conceals vital signs, visual effects, and electromagnetic spectrum frequencies detectable by the human eye. Instead, invisible entities utilize wavelengths such as radio, infrared, or ultraviolet, enhancing their ability to remain undetected.
What is the definition of invisibility cloak?
A cloak of invisibility is an object that shields the wearer from sight. Found in folklore, mythology, and fairy tales, this enchanted garment serves various roles, featuring as a tool wielded by deceptive characters or as an essential item worn by heroes on quests. It is a recurring theme in Welsh and Germanic folklore, possibly tracing its roots back to the cap of invisibility depicted in ancient Greek myths. This motif is categorized as “D1361.12 magic cloak of invisibility” in the Stith Thompson motif index scheme.
A real ‘invisibility cloak’ has been invented by Chinese scientists
Advancing technology to unprecedented heights, scientists have actualized the concept of Harry Potter’s invisibility cloak. Chu Junhao revealed this groundbreaking invention during the virtual event “Super Night of Science,” with subsequent footage circulating online.
In the clips, a man, accompanied by two assistants, showcases a life-size sheet of translucent material. The demonstration illustrates the cloak’s functionality, initially revealing the man’s legs in full view as they position the material in front of him.
Sources: Infotrend.com.ng
