Being involved in other things and not having written on this subject in a while - another attempt at summarizing the concept.
This study of light interaction with the retina of the eye has disclosed that this organ of vision evolved to detect light via a “classical/ quantum” physical mechanism wherein light is absorbed as the wave of classical physics in sub-optical wavelength spaces (“antennas”) between, and not within, the retinal cone and rod receptors themselves. These antenna sites must necessarily be, and are observed to be, located immediately adjacent to material specific, electron quantum confinement spaces (EQC) that are of constant dimension and are provided by the spatial structure of the rhodopsin/retinal complexes that are contained within the receptors themselves. I recognize that this view confounds the traditional “pure quantum” construction that photons interact with pigment molecules contained within receptors. To summarize this finding, wavelength discrimination in light interaction with matter is determined by spatial (or “nanospatial”) dimensionality.
Viewed in this manner the imaging retina of vision can be seen as an abstract array of quantum confined electron sites logically distributed in space. The classical wave-accepting inter-receptor spaces and the adjacent EQC regions form sub-micron dimensioned electromagnetic radiation detecting devices that are shown to be able, in the biologically evolved structure, to process both the intensity and phase of detected light and generate a signal measurable by the human nervous system. The spatial arrangment of the array of these devices on the retina shows conclusively (geometrically!) that this surface actually forms the Fourier plane of the optics of the eye. This conclusion has fundamental and far reaching consequences to our understanding of the vision process. A great deal of what has been left unexplained, or wrongly explained, in vision science is clarified by this finding.
I have described this light interaction mechanism as a “special type” of electromagnetic radiation detecting antenna structure because it is seen to have wave/particle nature. Such an interaction might alternatively be viewed as involving the plasmon (or “surface plasmon”) quasi-particle of solid state physics that is an abstract entity thought to have a similar dual nature. I would propose, however, that, going beyond abstract thought, this teaching of the retina allows for purposeful construction of nanostructural light interacting elements or devices.
Corroborating the above, this same mechanism has been shown in experimentation that I conducted to explain the recently discovered (Canham, 1991) phenomenon of an unexpected visible light interaction and resulting luminescence from a unique silicon surface nanostructure. I refer to what has been termed “porous silicon” (PS). This nanostructure is composed of an array of high aspect ratio “pillars” (or “webbing”) and intervening pores in the silicon surface with this nanostructure strangely resembling the receptor morphology of the biological retina! In PS experimentation it has been shown that visible light interaction occurs and only when the dimensionality of the silicon pillars is reduced to silicon-specific electron quantum confinement dimension, and, with this caveat, the wavelength absorbed (or emitted) is determined by the spatial dimensions of the intervening pores. It should be fascinating, and I have noted repeatedly, that this interaction with visible light occurs in an “inert” structure composed only silicon pillars and pores without a pigment molecule in sight!
But, building on the understanding of this mechanism, one can now go on to explain the reasons underlying the well understood capability of the biological retina for detecting and utilizing single photons*, and that this occurs, quite extraordinarily, at the elevated temperature of the human body.
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*In the spirit of the above I would rather use the terminology “quantized interaction” in place of the pure particle construction implied in “photon” but will use the latter term not to confuse things!
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One would then note that these single “antenna” interactions occur in the sub-micron (< 10-6 meters) spatial realm. This means that the retina contains an extraordinary 108 (or a hundred million!) receptors or light-accepting sites per square centimeter –a fact that is well documented in vision literature. One can then go on to consider each antenna site in electron device terms (the small capacitance characteristic of such an area, for example) with the conclusion that these are indeed very high speed electronic devices. A touch point to be noted regarding vision, derived from femtosecond (10-15 sec) spectrometry, is that that the signal-producing isomerization of the retinal molecule in retinal receptors occurs in the femtosecond time range. This certainly is evidence that the vision process at the retina involves this high speed (quantum) order of time. I have written much about this.
The other crucial consideration that must be considered in formulating such a high speed electronic device involves electronic noise or, more precisely, how is noise reduced to the level where the small photon generated signal can be discerned? In the field of solid state photonics such noise reduction is accomplished by cooling the detection system to cryogenic temperatures. A group of us noted in the 1970’s (and published with reference in the main body of the work) that such signal-obscuring electronic noise is a time integrated phenomenon with reduced time constant minimizing this unwanted factor. Electronic noise is composed of, generally uncorrelated, thermally generated electrons appearing in time. The shorter the time the smaller the number of such electrons integrated and the lower the electronic noise. I have proposed that operation in this short, femtosecond or less, time domain provides an explanation for the eye’s ability to detect single photons at body temperature.
Involved in other things and not having written about this in a while, this is another attempt at summarizing the matter:
A third and crucial ingredient necessary to complete the argument is that each high speed nanodevice of such an array is uniquely capable of detecting single photons (or quantized interactions) without the signal from any one event overlapping and potentially cancelling the signal from another interaction. This is readily calculable.
Single photon detection by the retina therefore results from heretofore unseen quantum spatio-temporal considerations. The vision process at the retinal surface must involve the disciple of quantum physics!
Taken together, this persuades me that light interaction in the eye occurs in the realm of quantum time and space and that the vision process – or the portion of it constrained to the retina – of necessity involves quantum physics.
GCH
9/3/07
