laser light

[Stefan Jeglinski <jeglin@4PI.COM>]

> Kock is a personal hero of mine just because he refuses to say that laser
> light is "in phase light" or "coherent light".


Why would he refuse to use terminology that is well-defined and in
fact a useful and even crucial way of distinguishing laser light from
incoherent sources? And why would that make him your hero? Just
because he believes he is bucking the trend? Fill me in here. You are
fond of accusing others of "demonization of the opponent" (recent
quote) when you believe they are being close-minded or too
establishmentarian, and yet you here appear to be foisting
misinformation that in a very subtle way demonizes those of us who
would in fact use very practical terminology from traditional schools
of thought. Jeez Bill, sometimes it's as if you got some chip on your
shoulder about those of us who got stupid PhDs or other "traditional"
degrees and sometimes have something to offer in the way of technical
knowledge.


> Instead he says that laser
> light is "sharper" than the light from other sources (which is exactly
> correct.


And so unbelievably vague that to use the term "exactly correct" is a
real disservice to everyone on this list.


> Point-source light can be focused nearly to a geometrical point,
> while the light from non-laser sources cannot.)


This is really sloppy at best. Laser light is not point-source, if
that is what you're implying. Virtually by definition, laser light
has a finite waist size.

And, even an ideal point source cannot be imaged to a geometrical
point (when you say "focused" you are likely to be talking about what
is seen in the image plane of a lens, but I am not sure - sloppy
terminology will kill you here). Check Goodman (or any decent text on
Fourier Optics). Convolution with a finite impulse response (true of
all actual lenses) prevents a geometrical point image.

Laser light leads to other effects because of its [typically]
gaussian spatial nature. I admit to not knowing who your man Kock is,
but I dare say that most if not all texts on Fourier Optics might as
well be burned if the unique properties of coherence were replaced
with the rubbish of "sharp." Get real. I'll keep Goodman because it
will allow me to get something done. You may dance with Kock and have
fun with those who don't use the word "sharp."

By the way, with enough apparatus, I believe one can make virtually
point-source sunlight that is highly collimated and also rather
coherent as well.


Stefan Jeglinski