Register  /  Login      

Towards the invisibility cloak – Photonick

By CoperNick

 Alice Gaggero

 

April 12, 2019

 

We have all envied Harry Potter’s invisibility cloak at least once. But it works with magic and unfortunately all of us are muggles. Instead, we can play around with science like some scientists are trying to do.

According to Science an invisibility cloak is a device that can create an optical illusion. To operate effectively, the cloaking device has to redirect all wavelengths of light. Until recently, the devices developed could only work within a narrow range of the light spectrum and therefore they were still visible.

In 2018 Luis Romero Cortés and his colleagues at the Institut National de la Recherche Scientifique—Énergie, Matériaux et Télécommunications (INRS-EMT) of Montreal, Canada, discovered a new method to distort light waves. The prototype created by Cortés is composed of two parts: one between the light source and the object, and one between the object and the observer. The first part redistributes the incoming wave energy to a region that is not affected by the interaction with the object. This is done by using an energy-preserving transformation. The transformation used is reversible, which means that the second part of the device will return the wave to its original form. Thus, the transformed wave will not interact with the object, and, in turn, will not be modified by it.

 

Fig.1. “Full-field broadband invisibility through reversible wave frequency-spectrum control.”

Credit: Luis Romero Cortés, Mohamed Seghilani, Reza Maram, and José Azaña

(a) The detection of a green object and its interaction with the spectrum of a broadband wave

(b) Concealing of the object by reversible transformation of the wave spectrum

(c) Numerical simulation of the proposed device with the effect of the transformation depicted like progressive processes although they are instantaneous.

 

As well as not being able to see the object, the observer will also not see the cloaking device: which is the real breakthrough.

The device is made of electro-optic components already available on the market. Each half of the device is composed of two electro-optic components. The first is a dispersive optic fiber, which makes the different wavelengths of white light to travel at different speeds. The second is a temporal frequency modulator, which modifies the light’s frequency while it travels through the device.

In Cortés’ work, the device was able to hide an optic fiber that absorbed specific optic frequencies. More tests are being conducted to ascertain if the device will still work for a more complex real-life object.

The device proves that it is possible to modify a continuous spectrum using the Talbot effect (a diffraction effect). This avoids using a periodic spectral phase filter, in which it is difficult to achieve a good spectral resolution. This method can be applied to a variety of fields: full-field spatio-temporal broadband invisibility; telecommunications; platforms which require the control of temporal and spectral phases of waves. In fact, this device works with a variety of wave types besides electromagnetic waves.

Research in this field is ongoing, and, while we are still far from achieving Harry Potter’s invisibility cloak, this is an important step in the right direction.

 

References:

Credit:

  • Luis Romero Cortés
  • Institut National de la Recherche Scientifique—Énergie, Matériaux et Télécommunications

 (INRS-EMT)

 

 

READ MORE ARTICLES AT THIS LINK