04-05-2012, 11:38 AM
NANOTECHNOLOGY in photonics communication
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INTRODUCTION
Einstein tells us nothing moves faster than light. In fact, it is so fast that as you approach the speed of light, time it itself starts to slow down. (Now that’s fast.) So when you want your email or your fax to get to somebody as soon as possible, what you really want to say is “get it there at the speed of light”. That is possible with our Photonics communication.
Tele communications utilize some of the various forms of light (radio waves or micro waves, for example) to throw information from one spot on the earth to another. With the billions of information flying over our heads every split second or passing below us in an optical cable, the whole world seems to be full of our thoughts. So full, in fact, that it takes a monstrous network of electric devices, cables and computers to keep it all sorted.
And sorting takes time. Even with the best electronics today sorting digital signals is not instantaneous, and every device, cable, or computer slows down the flow, even as it’s doing its appointed task of straightening all the signals out. The one that does all the work without taking any time at all is the perfect device. An all-optical router that could route the information without converting it from light to electricity is said to be the perfect device. The perfect device can be constructed using Nano technology in Photonics.
Manipulating Light with Crystals:
As our technology still seeks to increase the speed at which information travels, the scale gets global and we find the information super highway. Although the information super highway has often been used as just another name for the internet, it also describes the vast network of optical and electrical cables now used to carry information. Nano technology is set to take the next step and improve the highway again.
This over complicated, axed-out scene could use some simplifying. Crystals designed on the nano scale could replace electrical routers by directing the light itself instead of first converting it into electrical signals. The fiber-optic cables we use to carry information are potentially capable of transferring data at 10 to 40 Gbps. But most electrical routing occurs at less than 1% of that rate if we transfer to an all-optical router we could route most data packets in less than 1 trillionth of a second, pushing routing speed till it can handle the full capacity of the fiber-optic cable network.
Before we can look at the details of how such an all-optical router would work, we need to look at the nano- scale pieces of light that our crystals will be dealing with. These pieces are called photons and the science of manipulating such pieces of light is known as photonics.
Getting hooked on Photonics:
A photon is the smallest unit of light and doesn't really have a shape or size and mass. They are the building blocks of light and they travel normally in big groups. The information super highway requires orderly photons for information transmission. So, orderly photons have to be made before they can be used as signal carriers. The trick is photons can't really carry anything (as they are weightless) so they are not the messenger, they are also the message. By varying the number of photons we ca form a code of high and low pulses. When we work at the nano scale, we rarely encounter large mobs of photons instead; we have to deal with a few photons at a time. If our nano-crystal accidentally stops just one of the photons, we have immediately lost most of our information. Stopping light is ridiculously easy. Photons love to be absorbed by just about any thing. And those things that don’t absorb light usually reflect it. Thus the photon messenger must face getting either sucked up or bounced. Controlling where photons are absorbed and where they are deflected is the business of photonics and the concern of all nano-scale optical devices. Most of the time, we want those photons deflected as a means of moving information along a path, bouncing photons to their final destination. In order to do that we create and check the IDs for the photons.
Wavelengths: Creating nano-size IDs
The photons can be considered as a wave because they are vibrating and they can be considered as particle depending on the situation. Photons have detectable vibrations. In fact the length of the space it takes for them to go through one cycle of vibration determines the wavelength of a distinct bunch of photons. Moist of the light we dealt with as a wave length of few hundred nano meters. And it turns out that any nano-crystal router is going to have use the wave lengths of photons as a way to identify them. The nanoscopic crystal identifies different wavelengths of light by responding to how they travel. In fact different wavelengths of light travel at different angles when they are passing through a medium.
Optical communication is a pretty exclusive night club. Usually we allow only 1500 nano meter wavelength into the party because it’s the telecommunications standard wave length. So if crystal-based router s specifically designed to the 1500 nano meter wave length, it can be integrated into the inter net. It's important to note that different materials and crystal designs can be specifically tailored for a specific wavelength and only this specific wavelength excluding all others. That is if the photons don’t have the 1500nm ID, they cannot come into our communication system.
Controlling light: Photonic band gaps
Photons and electrons don’t have a lot in common but similar technology is needed to manipulate each of them. When we replace a slow electrical device with a quicker optical one the same old design can be used to generate ideas for the new one. To get semi transparent structures, we have to add just enough of the right impurities to our nano crystals. These semi transparent structures can be used to filter the photons. Since different photons have different wave lengths, by varying the geometry of the nano crystal, we can change which energies get stopped by the opaque part of the crystal and that pass through the transparent portion.
To understand controlling of light much better, imagine a large bowl with the marbles spinning around inside. Here the marbles are our photons and the bowl is the crystal.