Invisibility

In Star Trek IV: The Voyager Home, a Klingon battle cruisier is hijacked by the crew of the Enterprise. Unlike the starships in the Federation Star Fleet, The starships of the Klingon Empire have a secret "cloaking device" that renders them invisible to light or radar, so that the Klingon ships can sneak up behind the Federation starships and ambush them. This cloaking device has given the Klingon Empire a strategic advantage over the Federation of Planets.

Is such a device possible? Invisibility has long been one the marvels of science fiction and fantasy, from the pages of The Invisible Man, to the magic invisibility cloak of Harry Potter, or the one ring in The Lord of the Rings. For at least a century, physicist have dismissed the possibility of invisibility cloaks, stating flatly that they are impossible: They violate the laws of optics and do not conform to any of the known properties of matter.

But today, the impossible may become possible. New advances in "metamaterials" are forcing the major revision of optics textbooks. Working prototypes of such materials have actually been built in the laboratory, sparkling intense interest by the media, industry, and the military in making the visible become invisible.

Invisibility is perhaps one the oldest concepts in ancient mythology. Since the advent of recorded history, people who have been alone on a creepy night have been frightened by the invisible spirits of the dead, the souls of the long-departed lurking in the dark. The Greek hero perseus was able to slay the evil medusa armed with the helmet of invisibility. Military generals have dreamed of an invisibility cloaking device. being invisible, one could easily penetrate enemy lines and capture the enemy by surprise. Criminals could use invisibility to pull off spectacular robberies.

Discoveries behind "metamaterials"? Creation of metamaterials was once thought to be impossible because they violate the laws of optics. But in 2006 researchers at Duke university in Durham, North Carolina, and Imperial College in Longon successfully defied conventional wisdom and used metamaterials to make an object invisible to microwave radiation. For the first time in history, we now have a blue print to render ordinary objects invisible.

Metamaterials are substances that have optical properties not found in nature. Metamaterials are create by embedding tiny implants within a substance that force electromagnetic waves to bend un unorthodox ways. The result was a sophisticated mixture of ceramic, Teflon, fiber composites, and metal compounds. These tiny implants in the copper make it possible to bend and channel the path of microwave radiation in a specific way. Think about the way a river flows around a boulder. If the metamaterial can eliminate all the reflection and shadows, then it can render an object totally invisible to that form of radiation.

Metamaterials for light? One proposal is to use the off-the-shelf technology, that is, to borrow known techniques from the semiconductor industry to create new metamaterials. A technique called "photolithography" lies at the heart of the computer miniaturization and hence drives the computer revolution. Photolithography enables engineers to place hundreds of millions of tiny transistors onto a silicon no bigger than your thumb.

A milestone in the quest for invisibility came when this silicon wafer etching technology was used by a group of scientist to create the first metamaterial that operates in the visible range of red light.

The scientists first started with a glass sheet, and then deposited a thin layer of silver, magnesium fluoride and another layer of silver that is only 100nm thick. Then, using standard etching techniques, they create a grid pattern resembling a fishnet. The next step would be use this technology to create a metamaterial that would bend red light entirely around an object, rendering it invisible to that light.

The key to invisibility may be nanotechnology, that is, the ability to manipulate atomic-sized structures about a billionth of a meter across.

Given the enormous progress made so far in achieving invisibility, it clearly qualifies as a Class I impossibility. Within the next few decades to at least within this century, a form of invisibility may be become commonplace.