16 June 2011

Eye balls

Last week I was back in the lab again. A highlight of my time In Residence was sitting quietly drawing the experimental rig and an eye, while DT was back and forth conducting experiments on the ring resonator, answering my intermittent questions and explaining subtleties of the process. The setup was one that I am now familiar with, the laser light emitted from an electronic box on a raised shelf, passing through various optic fibres to the point where it meets the wafer, on a table that is damped from external vibration by means of hydraulic legs. The piece of silicon disc (wafer) is clamped down and the light carefully aligned along the microscopic silicon grooves and mounds etched within it to pass through, in this case, a ring resonator. This device modifies light. When first in the lab that sentence did not falter as it encountered my brain, but with time I am becoming more perplexed by the process of altering light; it seems a rather fundamental thing to do, even if technically simple, to change, for example, the wavelength of a ray of light.

The eye diagram is a standard output format for this type of work and is indicative of the level of clarity of binary information transfer, a widely open eye being a sign of good data transfer with a low error rate. DT has recently used one of his silicon photonics devices to transmit data at 40Gbit per second (with a modulation depth up to 10dB, which may be of interest to the initiated), which is pretty quick. (see http://www.opticsinfobase.org/oe/abstract.cfm?uri=oe-19-12-11507 for the paper) (Incidentally, “pretty quick” in the former sentence actually means unprecedentedly fast rates for optical modulation in silicon with a large modulation depth, and hence also useful in a practical sense). The eye was all seeing as I drew.

But it’s not all work. The lab meeting that I attend the next day is followed by a group tennis doubles tournament. My partner and I are the unrivalled losers, but strangely are the only pair to take a game off the boss and second in command (who, weirdly since they are the two best players, were drawn (by the second in command) to play together) – I think that we discombobulated them with our atrociousness. Or maybe it was simple pity (although I’m not convinced by this second suggestion, the boss has a penchant for fiendish spin which, when on the receiving end of it, doesn’t seem to have any possible connection with pity). (Is it possible that it is connected to the spintronics I’ve heard mention of around the ATI?)

As ever my return home is in a state of mental disintegration – the transition between these two worlds seems to have the kind of impact on me that I imagine teleportation would. And the tang of tennis weary legs on the train is a physical memory, reminding me that it seems I need to work on my tennis as well as my maths.

7 June 2011

Potential realities

The estuary at St Germans as stunning as ever, the bright sun glinting from the freshly rain-touched greenery and the river; the Tamar. Separating Cornwall from the rest of the country the beautiful inlets and waterways coming to a head, from the perspective of the train at least, as we pass over the Brunel Bridge at Saltash, and out to the sea beyond. As we cross the bridge I leave behind the gentle comforts of home, and pass the ‘realities’ of militarisation, dockyards, the urbanisation of Plymouth, heading into other versions of the world beyond, up country.

I have started reading Werner Heisenberg’s ‘Physics and Philosophy’, first published in 1962. In the late 1920s Heisenberg was famously uncertain about the possibility of knowing where anything is and the concurrent speed at which it is travelling, although, apparently paradoxically, was able to accurately know the probabilities of these attributes. Einstein was unconvinced by the idea of this fundamental unpredictability in the physical world, famously retorting “God does not play dice with the universe” to the notion. Heisenberg’s view, known as the Copenhagen interpretation of quantum mechanics, tells us that the observations of, for example, an electron, are what result in the existence of the electron. Measurement of the position of an electron creates an electron-with-a-position; test its momentum and an electron-with-momentum is created. An electron, in this view, is not a physical entity, but it and other fundamental particles “form a world of potentialities or possibilities rather than one of things or facts”. The reality, apparently, is the observation, not the electron.

And with such thoughts and words I am firmly back on my path into the world of electronic physics, striding out as if wearing high platform shoes with super-wobbly blancmange soles. Off I lurch, to observe the silicon photonics laboratory, wondering what art realities will result. It sure is good to be back.