All of us on this board will be familiar with the physical phenomenon known as light. What may be less well known is its importance to the PTK project. In my view, the speed of a POET or PET chip, its coolness of operation, its ease and relative cheapness of manufacture are all major assets. It is its capacity to manipulate light that is its greatest asset and my intention in this post is to convince you why. Also, remember, in the past, POET was a company that was originally a manufacturer of solar equipment and the Geoff Taylor input was in the control of these. It was after the withdrawal of government investment in such technology that the company experienced its difficulties and changed direction.

Whether you realise it or not, light is a remarkable physical property. Atomic theory envisages light in the concept of the photon. This theory has developed from the start of the 20th century when Albert Einstein described the photoelectric effect (light striking certain materials could induce an electric current and he showed that this effect meant that light was particulate). Isaac Newton postulated this in the 16th century, in the 19th light was considered a wave because of some of its behaviour. Modern theory has come up with the concept of duality, that light is a packet of energy with both wave and particle behaviour, this later became named the photon. It is considered a fundamental entity, i.e. it cannot be broken into smaller components.

Light has a velocity (30,000,000 metres per second approximately) in a vacuum. If you divide this number by the medium’s refractive index you can get its velocity in air, water, glass etc. That means a photon will travel in a straight line at that velocity. In glass, such as a fibreoptic cable, at about 2/3 of that velocity, that is very, very fast. Not only that, photons transfer very little of their energy to the medium in which they travel and so transfer is cool and fast, significantly faster than electron transfer in a wire (also known as an electric current). This fact means that light transfer of information is inherently faster and cooler, physics dictates that.

When a photon hits the retina of your eye it induces a nerve impulse to your brain which interprets an image. The photon is a wave and has a wavelength and that determines the colour you see, lots of photons mean more intense light and different colours and so an image is rapidly built up.

What you may not realise is that nothing in the known universe travels faster that a photon and Einstein’s Relativity theory (which explains every known physical phenomenon very accurately) is dependent on that. This produces counter-intuitive properties. In the early 20th century, he was a patent officer in Bern, Switzerland and travelled home by tram from the office. He used to look at the city clock tower and imagine what happened to the time as the clock receded in the distance. He thought that if he could travel away from the clock at the speed of light, the time would not change, he would only see the photons that left the clock as he started. Yet, someone outside would see the clock ticking away and time changing and his watch would tick away too and time would change. It was this hazy idea of variable time frames that inspired his general theory of Relativity whose primary concept is that time is not fixed, it changes with relative velocity. Thus the Newtonian idea of fixed time for all objects throughout the universe could not be right. It is sufficient to tell you that Newtonian physics can still be used because our relative velocities’, in normal experience, is extremely small and doesn’t alter the mathematics in any significant way.

I digress, because I must tell you one other fact. Light is binary phenomenon, it is either no light or it is light, off/on. So, if you have off and on, you have 0 and 1 and can transfer any information as a binary number – remember those – 0,1,10,11,100,101,111,1000 equals 0,1,2, 3, 4, 5, 6, 7, etc. So light can transfer numbers very fast and very cooly. Here is the hidden secret of POET; Silicon can’t do this on chip. We are awaiting the VCSEL announcement. That is a Vertical Cavity Surface Emitting Laser. Most chips emit signal from their edge but a VCSEL emits from the flat surface of a chip, it make connection to the outside easier and more sophisticated. And, because you can do lots of other things in a chip, like processing numbers, flexible and comprehensive memory etc. you can convert any signal generated into light and transfer this at the fastest speed known in the universe. This is why the new CEO thinks the future lies with opto-electronics.

Silicon controlled lasers have to transfer information by wire to other parts of a circuit board to generate the light signal and then transfer elsewhere; it can’t do the on-chip function. Less components, cheaper and ground breaking. So you end up with a very fast, very cool microchip that can give you light or electronic signals on a single chip. We are at the tipping point. Brilliant uh!

David