Playing With The Speed of Light!

 Playing With the Speed of Light!

SAM Daily Times

When sending light pulses along a transmission cable, Engineers sometimes need to slow down one pulse with respect to another.This is normally achieved by using numerous optical fibres, all for the same very purpose. However, studies and developments in science have now revealed that a small cell containing hot Rubidium Gas can serve the purpose much more effficiently and with much less complexity.How?

The discovery of  making light travel at a speed lesser than that of light !  Normally traveling at 300m/s, light, when passes through a transparent medium such as glass or water, retards a bit, reason being , the very weak interaction of photons with particles of the medium. However,any efforts to slow down the speed at this stage will result in light being absorbed by the material.

Per Contra, Professor George Welch, Texas , A&M University , devised another way,using the technique called EIT ( Electromagnetically Induced Transparency). Here, "a laser manipulates the quantum states in an opaque cloud of atoms and makes them transparent to a narrow range of wavelengths of light. According to electromagnetic theory, this narrow transmission band leads directly to an index of refraction that depends strongly on wavelength in this range".Prior studies had told researchers that "Wavelength-dependent phase velocity causes the light's "group velocity"--the speed at which energy and all signals travel--to slow by more than one hundred times"




              

The tiny light slowing chip: two chambers with Rubidium atoms inside;the whole thing smaller tahn a coin!

In his experiment, Welch brought two pulses of light , wavelengths lamda1 and lamda2, together, to interact with each other, inside a transparent container of Rubidium Gas, previously heated upto the boiling temperature of water. A third, much longer pulse, of wavelength lamda 3, was produced, its speed, much lesser than either of the ones producing it. In a series of different experiments , conducted between 1999 to 2001 (Harvard being one of the universities involved), speeds as low as 90m/s were achieved.

This  "putting the brakes on light" discovery can do wonders in the field of science and technology. Apart from the one I mentioned right in the begining ,a very cheap source of UV light that can read concentrated bits of data on CDs, is another "just a very small example". The controlled movement of photons to store , process data shall also pave way for further advances in the development of Quantum Computers; extermely powerful mathematical machines, capable of searching huge databases most efficiently, performing complex mathematical calculations ,very important for efficient encoding and decoding of data and lot more.