In our times, the Big Bang Theory is generally accepted to be the starting point of the universe. When the Big Bang happened, the universe and light were simultaneously created. The universe came into being at elevated temperatures from a single particle.

For the events that happened after the Big Bang, the most recent and accepted theory is the Inflation Theory. According to this theory, right after the Big Bang, the universe started inflating at an incredible rate, quantum fluctuations were scattered throughout the universe, and a homogenous inflation happened which allowed galaxies to be formed. Light was created at this period for the very first time.

What is “light” and what is the wisdom behind it?

Ibn Sina was the first scientist stating is was possible to measure the speed of light. And Newton used the marble example to explain the phenomenon of light containing colors of different wavelengths. Modern theories state that light is composed of weightless and charge-less particles called photons. Light is now known to be electromagnetic waves that carry energy as well as having the characteristics of refraction and reflection. A major discovery occurred in 1975, when the Danish scientist Ole Romer was observing the satellites of Jupiter. During this study, he was able to prove that the particle model proved to be insufficient, as was seen from the diffraction of light (changing its direction after having passed a narrow slit)..

Although the wave model is more dominantly talked about in modern times, it is known that both models are true.

Femto photography

Various experiments have been done to understand the properties of light. One of these experiments was a photography technique applied by Dr. Edgerton, in 1964. In this photo, the image of the apple right after the bullet passed through it was captured. This famous photograph, which was captured in a millionth of a second, inspired Prof. Ramesh Raskar from MIT (USA) to take a photo of light in order to see it by naked eye. Raskar developed a camera that can take up to a trillion frames per second. This would make it possible to visualize the human body without using X-ray. The wave like property of light was studied by this new technology called Femto Photography.

Light is the fastest substance in the universe. As long as it does not change its environment, the movement of light is linear because of its electromagnetic wave properties. If it passes to a different but transparent environment, it continues its movement. If it passes to an environment where the refractive index is larger than its original environment, it comes closer to the line accepted to be vertical to the surface (normal) and vice versa.

The speed of light and all electromagnetic waves in an empty, airless environment is 299,792,458 m/s (300 thousands kilometers). With this incredible speed, the Earth could be toured 7 times a second. The letter c represents this speed in science, and it’s based on the Latin name for speed: celeritas. While passing through any object (air, water, glass etc.) the speed of light is smaller than c.

If a laser pointer is activated for a thousandth of a second (a couple of femto seconds), a photon cluster is formed which is approximately 1 mm in width. This cluster of photons has a speed millions of times greater than the bullet passing through the apple.

What if the femto photo of a cluster of photons that were sent from the bottom of a glass bottle full of water was taken? How would the light appear in slow motion? Although this short journey of light takes place in less than a nano-second, it is possible to capture how it moves in slow motion by reducing the speed ten billion times with the femto camera. With this femto camera, it is possible to measure the average speed of light in a tomato and gain knowledge about its interior texture and quality without touching it. When a bunch of photons are sent to the surface of a sample, a three dimensional picture of it can be constructed by the high resolution detection of the photons that are reflected at different times from the sample.

With the science of light, technology for transportation that does not require a driver can be developed, creatures can be saved from natural disasters by the reflection of light on windows, and many new age surgery technologies can be developed.

In order for the eye to see, light needs to exist. One of the latest and most astonishing pieces of research done about light is the femto photography technology. By this technology, it will be possible to visualize the human body without the use of X-ray. If there was a femto camera incorporated in our cell phones, we would be able to understand the quality of the tomatoes we were buying when we went to the grocery store without having to touch them. By harnessing the great gift of light, we can make the great gift of life even better.

WHY OPTICAL?

Despite the many benefits that classical computers (‘classical’ here means computers in which the signals are carried electrically) have brought to our lives, they have some limitations which prevent any improvement in the speed or volume of signals carried. These limitations are inherent to the way these computers work.

For example, classic electric circuits carry information units serially, one by one, and there are some lower limits beyond which such circuits cannot be built-below that limit they simply cannot process the information reliably. Another handicap is that electrons floating in circuits can interfere with each other-and this interference, incidentally, is one reason why engineers cannot produce smaller circuits. By contrast, photons, light particles, which are the main signal or information carrying agent simply do not interact with each other because they do not carry a charge.

An optical computer could be run faster than one running electrons, theoretically at the speed of light, along optical fibres which are specifically designed guide-wires to transfer light-photons in and out between chips in an optical computer without distortion.

One of the main advantages of optical computers is their capability of processing more than one piece of information at the same moment. That means multi-beams can be processed in one chip. This would allow engineers to use parallel processing which greatly enhances the speed of the computer.

THE DIFFICULTIES

Lasers would, naturally, be the source of light in this new generation of computers. Scientists and engineers all over the world are trying to build appropriately tiny lasers emitting precise frequencies of infrared light. But they face a number of practical hurdles. One has to do with making lasers of appropriate size and efficiency. Current technology does not have the means to build optical chips comparable in size to ‘classical’ ones. The efficiency of the lasers is not high enough for the specifications required. Most of the energy to run these lasers escapes as heat and is not used. Since one or at most two percent of this energy can be transformed into the useful form of light, the rest can generate a lot of heat which is dangerous to the condition of the chips.

Making the right lasers is not the only problem on the way to fully optical computers. Switches are at the heart of optical computers, but as photons do not interact with each other, there are substaintial difficulties in building switches.

SOME PROPOSED SOLUTIONS

One solution to this problem is to build computers which are part electrical, part optical. Many scientists now believe that the most viable use for optical technology is in this type of hybrid system combining optics and electronics. Researchers are now focusing their work on optical interconnections between chips, which could be a reality in as little as one or two years. This type of connection can vastly increase the amount of data moving in and out of chips.

Such a machine would have to contain prisms, mirrors, and lasers to channel the light, as well as gallium arsenide chips that convert pulses of laser light into electrons so as to function as switches. If all this does happen, there will be a need for new computer architectures, that is, new computer structures.

However, there are some scientists following a different route. They are trying to find ways to use current transistor technology so as to detect laser beams in the information processing. NPN type transistors without a metal cover would be appropriate because they are faster. This approach also allows for adaptation of existing designs, with all the advantages in time and savings that brings.

FUTURE

The first optical processor developed at AT&T Bell Labs measured about two feet by two feet. Scientists hope some day to fit it all into three square inches. A fully optical computer is more than five years away.

Scientists have set themselves a target for the year 2000: 1,000 I/O (input and output) channels running at 1 giga-bit/sec. That is a thousand times faster than current modern computers.

It is a pity that we must wait for a decade, while scientists and engineers try to accomplish this difficult task. But what an exciting wait!

•  FURTHER READING
• ‘Bright future’, Scientific American, May 1990.
• ‘Now easier optical’, Electronics, May 1990.
• ‘Slacken lights up’, Scientific American, July 1991.
• ‘Optical computer no longer lighters away’, Byte, April 1992.
• ‘Optical computing sheds ‘blue sky’ image’ Electronics, April 1990.