New light

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.

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 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.

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.