Is invisibility possible?

1. 1
Is Invisibility
Possible?
Ang GAO Ecole des mines de Saint-Etienne

2. 2
Outline
 How does it work in science fiction?
 Is it possible in science?
 What is light?
 How does light interact with objects?
 Can we bend light?
 Realization1 : metamaterials
 Realization2 :transformation optics
 Applications
 Conclusion

3. 3
How does it work in science fiction?

4. 4
Is it possible in science?
David Smith
Duke University
Professor of electrical
and computer engineering
“A true invisibility cloak IS possible within the laws
of physics.”
Yes, it is possible!

5. 5
What is Light?
An electromagnetic wave, made up of different wavelengths.
380~780nm visible light

6. 6
How does light interact with objects?
Invisibility refers to an object which neither reflects nor
absorbs light.
Invisibility refers to an object which neither reflects nor
absorbs light.
Reflection
Absorption
Transmission

7. 7
Can we bend light?
Yes -
Refraction!
Refraction law : n1sinθ1=n2sinθ2
n: refractive index n>0
If n1>n2, then θ1<θ2; If n1<n2, then θ1>θ2; But that will not change the direction of ray.
Refraction law : n1sinθ1=n2sinθ2
n: refractive index n>0
If n1>n2, then θ1<θ2; If n1<n2, then θ1>θ2; But that will not change the direction of ray.

8. 8
Can we bend light as we want?
The cloaked zone is invisible!

9. 9
Archievement 1: metamaterials
Metamaterials have properties of NEGATIVE refractive index.
Metamaterials contain tiny implants which can control the refractive
index at every point in a material.
This would enable light to bend in a path around an object

10. 10
Archievement 2: transformation
optics
• Fourier Transformation
• To change the coordinate system out of Cartesian

11. 11
Archievement 2: transformation
optics
An experience in optical invisibility

12. 12
Applications
 Cloaking military devices
Invisible soldiers, airplanes, tanks....
 Diagnosing Disease
Improving medical imaging by cloaking internal organs and tissue
 Computing faster
photonic computer chips replace of electronic computer chips
 Harvesting Energy
A system using negative materials that will harvest light on the
scale of a wavelength
 Magic, art, fashion show

13. 13
Conclusion

Is invisibility possible? ----> Yes!

Is invisibility simple to accomplish? ---> No!
However, we have already realised the 2D invisibility, we created the
special material--->metamaterial which has a lot of
applications.
Technology can change the world
We are on the way to the 3D
invisibility...

14. 14
THANK YOU FOR YOUR ATTENTION!
ANY QUESTIONS?