Jump to content
Washington DC Message Boards

Invisibility cloak renders objects invisible to near-infrared light

Guest Xiang Zhang

Recommended Posts

Guest Xiang Zhang

Scientists have taken a step further in making an invisibility cloak by developing a material that renders objects invisible to near-infrared light.


A major step towards the realization of invisibility in the visible region is reported online this week in Nature Materials. The study demonstrates cloaking in the optical region for wavelengths in the near-infrared part of the spectrum and moves us a step closer to invisibility in a region that can been seen by humans.


Although cloaking has been demonstrated recently for the microwave region, the device structure used for these cloaks makes scaling down to the small wavelengths of the visible region challenging. Xiang Zhang and colleagues have now achieved cloaking in the optical region by etching small nanoscale holes into a layer of silicon. The holes follow a complex pattern and are designed to hide an object underneath a small bump -- creating a so-called carpet cloak. Compared with previous realizations of cloaking, the present design shows low losses and broadband operation over a wide part of the near-infrared spectrum. This design also has the potential to re


adily scale towards the visible region.


"So by manipulating the optical density of an object, you can transform the light path from a straight line to any path you want," he added.


The new material produces such an effect through a series of minuscule holes strategically "drilled" into a sheet of silicon.





Link to comment
Share on other sites

  • 2 years later...

Harry Potter's invisibility cloak is now becoming reality.



The single-beam mirage effect, also known as photothermal deflection, is studied using a free-standing, highly aligned carbon nanotube aerogel sheet as the heat source. The extremely low thermal capacitance and high heat transfer ability of these transparent forest-drawn carbon nanotube sheets enables high frequency modulation of sheet temperature over an enormous temperature range, thereby providing a sharp, rapidly changing gradient of refractive index in the surrounding liquid or gas. The advantages of temperature modulation using carbon nanotube sheets are multiple: in inert gases the temperature can reach > 2500 K; the obtained frequency range for photothermal modulation is ~ 100 kHz in gases and over 100 Hz in high refractive index liquids; and the heat source is transparent for optical and acoustical waves. Unlike for conventional heat sources for photothermal deflection, the intensity and phase of the thermally modulated beam component linearly depends upon the beam-to-sheet separation over a wide range of distances. This aspect enables convenient measurements of accurate values for thermal diffusivity and the temperature dependence of refractive index for both liquids and gases. The remarkable performance of nanotube sheets suggests possible applications as photo-deflectors and for switchable invisibility cloaks, and provides useful insights into their use as thermoacoustic projectors and sonar. Visibility cloaking is demonstrated in a liquid.



Edited by Luke_Wilbur
Link to comment
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

  • Create New...