I Tom;
I was thinking more on this after I posted and realized just what you
are saying. I asked myself ok what if heterodynes
<http://en.wikipedia.org/wiki/Heterodyne> were generated
in some object smaller than a micron and I was looking at it with a
conventional microscope. I suppose that I would see a light source but
I wouldn't be able to resolve it's shape due to the limitations of the
optics. More comments below...
Thomas Kelly wrote:
Joe,
You wrote:
"This would produce harmonic mixing and would result in the
generation of two new wavelengths which are the sum and difference
frequencies of the original light sources."
I don't plan to try it at home, but I don't doubt this to be true.
I can't see how stimulating an organism to emit light would get
around the difficulties of resolution at magnifications necessary to
see viruses .... alive or not.
Organisms that emit light naturally are still subject to the
limitations nature seems to have imposed on our various light
microscopes. Fluoroscopic techniques .... binding fluorescent
antibodies to cells ... allows for ID/sorting of cells
including microbes, but the glowing cells can only be magnified to
about 1000X (light microscope) 1400X with UV microscopes.
Exactly.
I am curious about the "harmonic mixing" you refer to.
The monochromatic light sources .... laser generated?
They could be although they wouldn't have to be monochromatic. A broad
band light source containing spectral components that are suitably
spaced to create the difference frequency we need ( in the visible
spectrum) would work fine. So then I asked myself why I have never seen
anything curious like this. We were talking about mixing two UV
wavelengths (due to the ability of the short wavelengths to offer
superior resolution) but if harmonic mixing could take place as we are
talking about it could happen with wavelengths from any part of the
visible or invisible spectrum. Your typical optical scope uses a
halogen bulb which is a heavy radiator in the infrared. Harmonic mixing
of sub visible spectra should result in heterodynes (sum frequencies) up
in the visible. I mean light from the infrared end ( say 900 nm) could
mix with light from the UV end ( say 400 nm) to result in a difference
frequency of 450 THz which would have a wavelength of 660 nm right in
the red wavelength area of the visible spectrum. So why has no-one
noticed this? The answer is probably due to switching speed. In a
semiconducting junction pairs of charge carriers are formed when a
current flows. When the wave polarity reverses these charge carriers
have to move to prevent current flow in the opposite direction ( this is
the essence of the switching action which IS the non linearity which
creates the heterodyne effect) If the charge carriers cannot move fast
enough in the material to perform this function then the material will
not act as a harmonic mixer. Switching speeds would have to be
exceedingly fast to heterodyne light. For example for a 500nm
wavelength ( mid visible spectrum) the frequency of this light wave
would be 600 e12 Hz! (THz) The fastest semiconductors manufactured are
about 10 000 times slower than this (60 Ghz to maybe 100 Ghz).
Superconducting josephson junctions are touted to be about ten times
faster than conventional semiconductors but that still only gets us up
to 1 THz. I was initially wondering if something in a DNA strand could
act as a switch at these frequencies but of course if it were possible
we would see the colours of the rainbow emmanating from some points in
the cell nucleus which would be too small to resolve. The world would
probably look quite different if harmonic mixing of light was happening
anywhere!
Only two wavelengths generated? .... one the sum and one the
difference of the original wavelengths .... No heat?
Some heat would be dissipated as there are always losses in materials.
The amount would equal the energy in the incoming spectra minus the
energy in the radiated spectra.
I ask about the heat because the brightness of the field of view
of a microscope is inversely proportional to the magnification. At
6000X a very high illumination, or emission of light would be
necessary in order to see anything. Heat could be bad.
Would the object continue to emit light after the sources were
stopped (a la glow in the dark frisbees ... electrons doing quantum
leaps)? Would there be pulses or continuous flow?
No the radiated light would only be the result of mixing of components
in the incomming spectra. It would be continuous if the lamp was on
continuously.
"This would require that both the source waves be focused onto a
point whch has the property of a semiconducting junction ."
The points we are referring to are microscopic ..... a trillion
viruses in a period (New Times Roman 12) at the end of a sentence.
I'm only asking, Joe .... Is it reasonably possible to achieve
harmonic mixing on a microscope slide and would it somehow allow for
magnifications, using glass lenses, that are not achievable w/o it?
Now that I have thought about it more I guess the answer is no.
Joe
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