Today a full day of physical work; gratifyingly tired. I am reduced to sitting on the floor to write as I don’t have the heart to shift either of the cats who are inhabiting the newly arrived chairs. His and hers, crashed out next to the stove. (I think that M + T, the kind chair donors, will feel that this is the appropriate hierarchy of users.)
It’s dark and tonight’s scene is illuminated only by the light from the laptop screen and numerous flames, both naked and encased behind the mica windows of the aforementioned sizzling stove.
The book lies open at a page showing the title of section 2.3.
Phase of a propagating wave and its wavevector.
I can’t tell if it’s merely the rhythm of the words, or a combination of that with their subtle rhyme and alliteration, but I cannot help but roll the phrase around in my mouth for a while, feeling its sound. It feels good. And visually the veve (vera verity?) embedded in the last word is somehow both alien, and yet unspeakably perfect.
Yesterday I spent much of the day with the book, revisiting things that I had glancingly encountered previously. I was making notes, reading around, and more fully understanding ideas that were being described to me. I realised I’d previously totally overcomplicated the notion of phase. What is phase? (– it helps, when dealing with this question, not to worry about wave particle duality implications, but just to consider light in terms of its wave properties - in my experience this shifts the understanding from mind-bendingly impossibly complicated to really pretty straightforward). It also helps to consider that the time element involved is fundamental – phase is the proportion of a periodic waveform that passes some reference point after a time t. Simple. So, on I skipped, frankly even feeling a little bit smug at how readily it was all going in this time. But.
Amazing that the simple act of turning a page can move one from lackadaisical absorption and regurgitation of information, into utter incomprehension. That thin layer from page 13 to page 14 has a sharp edge, and is followed by some maths. I stumbled around with a number of the equations, which I didn’t follow but felt that I should, and which culminated with the rather uncompromising words:
“Clearly this implies that:
r = 1
and that r is also complex and hence a phase shift is imposed on the reflected wave.”
I’m afraid the only thing clear to me at that moment was that clarity and I had parted company. (Maybe this ‘clearly’, as with other transparencies, is a relative term, and I simply had some kind of nonlinear response to the information such that my optical density increased with the intensity of the mathematics). But I do not wish to infer that the writings of Reed and Knights (or “the boss” as the former is currently known among intimate company) are in any way at fault – only moments earlier I had been applauding the inclusiveness of their fundamental introductions to various aspects of the subject. No, rather it was that the brain of the resident artist was not at its best, and seemed to fall at what is shamefacedly probably quite an easy hurdle.
An urgent injection of low brow was required so I returned to wiki, in an effort to ease the pressure on my head.
The wiki silicon photonics page is not exactly what I would describe as low brow, and when I reach the statement that two-photon absorption “ ...is related to the Kerr effect, and by analogy with complex refractive index, can be thought of as the imaginary-part of a complex Kerr nonlinearity. At the 1.55 micrometre telecommunication wavelength, this imaginary part is approximately 10% of the real part.”, I decide that my efforts into comprehension of this realm are probably done for the day. I take a morsel of comfort from thinking that at least I get a little of what a wavelength of 1.55 microns implies, but my brain falters at trying to compute how one can calculate the size of an imaginary nonlinearity, let alone as a percentage of reality.