New light

New light

The latest researches revealed new properties and behavior of light that were unknown to us.
If we could devise new techniques to apply this knowledge of light, then it might bring huge changes to our future lives.
Here we introduce the surprising “New Light” which is grabbing a lot of attention lately.

Droplets of light

Light that stays around a hole
and does not fly away

Light can pass through even small holes. But what happens if you make that hole smaller and smaller? Actually, light cannot pass through holes made smaller than certain size. That certain size is determined by the wavelength (color) of the light. Take a close look around the hole at this point. The light appears to be seeping out slightly from the hole. But the light is not going anywhere. So now we have light that does not fly away. This light looks like a water drop hanging from a water faucet. This kind of light is called evanescent light. Use of evanescent light allows you to observe objects too small to be seen by ordinary light or record incredibly large amount of video on a DVD or Blu-ray Disc.

Evanescent light
Evanescent light

Color of light

Color changes by size and shape

Do you know how the red color of stained glass is made? The answer is gold. However, the color emitted from gold should be gold just as a color of a gold nugget.
So then why does the stained glass appear red?  Actually, the gold is mixed into the stained glass as tiny particles. Their size is about one billionth of a meter. This shows us that various colors can be created by changing the size and shape of material in this way. Color is defined by the reaction between light and matter. Even for the same material, light reacts in a completely differently way depending on the size and shape of the material.

The gold used for stained glass appears “red”
The gold used for stained glass appears “red”
The gold nuggets appear “gold”
The gold nuggets appear “gold”

Crystal of light (Photonic crystal)

What is the actual color?
Strange colors that change
with viewing angle

The color of a material is defined by pigment. However, in a structure called photonic crystal, the color is determined by the size and shape of the object. This color is called structural color. The artificial opal and artificial jewel beetle shown in the photo are made from photonic crystal having a periodic structure with a light wavelength (color) of less than one millionth of a meter. The photonic crystal is a material that not only changes color but also confines the photons and atoms, and generates a doughnut shaped laser beam so that it will likely have a vast range of applications in various optical devices.

artificial jewel beetle
artificial jewel beetle
artificial Opal
artificial opal

Metamaterial (Invisible cloak)

Bending light
might make you an “invisible man”!?

Metamaterial is a substance like photonic crystal that has a structure allowing light to be freely manipulated as needed. Metamaterial is an artificial substance that is not found in nature, fabricated from small structures such as metal and is capable of manipulating reflection and refraction of light beyond commonsense in ordinary world. Utilizing metamaterials may allow making an invisible cloak like those often seen in movies and animations. Wrapping an object you want to make invisible with metamaterial, causes bending of light rays coming from rearward that make the wrapped object appear invisible.

Metamaterial (Invisible cloak)
Metamaterial (Invisible cloak)

Optical tweezers

Grabbing an object with light

In a science fiction movie, you may have seen a light beam grabbing and pulling an object. In the world of light, such a technique is used as so-called “optical tweezers.” In microscopes, a laser beam is focused and applied on a tiny object. A light pressure and a gradient force act to grab the object when the two forces are in balance. Optical tweezers can control the motion of objects without directly touching them and are used in a wide range of application such as biology, medical treatment, and chemistry.

Grabbing an object with light
Grabbing an object with light
Optical tweezers
Optical tweezers

Twisted light

Rotating objects in a vortex of light

Waves in ordinary light travel like waves on the ocean and are called plane waves. On the other hand, there is a light called a Laguerre-Gaussian beam that appears in a twisted spiral shape. Projecting this light on a wall forms a ring shape like a doughnut. The flow of the energy is also in a spiral shape so that small objects can be rotated by irradiating this light on the object. This technology to control the rotation of objects without actually touching them is called an optical torque wrench.

Ordinary light wave(plane wave)
Ordinary light wave(plane wave)
Twisted light wave (Laguerre-Gaussian beam)
Twisted light wave (Laguerre-Gaussian beam)
Optical torque wrench
Optical torque wrench
[Supervisor]
Yoshiyuki OHTAKE
Central Research Laboratory, Hamamatsu Photonics K.K.
Specialized field : Quantum electronics, Quantum optics, Optical physics.