From: et@teal.csn.org (Eric H. Taylor)
Newsgroups: alt.sci.physics.new-theories
Subject: Re: Good Things come in Big Bangs
Summary: Uncertainty? Just Say No!
Keywords: uncertainty, lasers, photons, femto-seconds
Date: 26 Aug 92 04:22:16 GMT
Expires: Sat, 19 Sep 1992 06:00:00 GMT
Followup-To: et@et.com
Distribution: na
Organization: Eric Taylor and Associates Inc

In article <16sicfINNss@darkstar.UCSC.EDU> gross@maxwell.ucsc.edu (Mike Gross) writes:
>In <92231.182704A54SI@CUNYVM.BITNET> A54SI@CUNYVM.BITNET writes:
>
>
>> Concerning what a frame of reference travelling at c with respect to another
>>frame, an earlier post answers it using more SR than I know yet.
>
>> Concerning photons as marbles, I'm not sure that they can be sufficiently
>>localized like that. A photon is an energy level of a quantized harmonic
>>oscillator, which by mathematical analogy, can be related to a radiation field
>>but it is not a chunk of light spatially localizable -- from what I can glean
>>from the incomplete and contradictory utterances of many professors and books.

I'll send you some better info. Keep in mind that we are not trying to
localize it, just describe it.

>>-------
>>CHARLES HOPE   A54SI@CUNYVM   A54SI@CUNYVM.CUNY.EDU
>>BUSH IN 92: ENVIRONMENT, EDUCATION, AND NO NEW TAXES.

Why change Bush in the middle of a screw? Vote for George in '92.

>
>You are correct that it is not possible to model a photon as a marble, but
>your reason is not quite right (it's close). One can understand a photon as
>an energy level of a quantized harmonic oscillator--this is in fact the 
>standard interpretation. This is equivalent to knowing the photon's frequency
>(and therefore its momentum) exactly. By the Uncertainty Principle, your
>uncertainty in position is therefore infinite. But you can play the opposite
>game. You can _measure_ the position of the photon, but then you have no
>idea what it's frequency is. One of the cutest demonstrations of this is a
>picture of a femtosecond laser, if you can get ahold of it. Light travels at
>about a foot per nanosecond, so the length of a femtosecond pulse is about
>1/100 inch. This localization is enough to make the laser appear far from
>monochromatic.
>
>A more standard explanation is that if you consider a double slit experiment,
>and you try to determine which slit a photon passes through, you destroy the
>interference pattern (recall that the pattern is determined by the wavelength).
>
>
>Mike Gross
>Physics Board
>Univ of California                   GO SLUGS!!!!!
>Santa Cruz, CA 95064
>gross@maxwell.ucsc.edu
>

A femtosecond laser? Interesting notion. Let's consider it.

What is a femto?
A femtometer (fm) is 10^-15 meters (m) (from the Swedish femton = 15).

A nucleon is spherical to the first approximation, and the nuclear
radius (R) is given by:

R = r0 * A ^ (1/3)

where r0 = 1.2 fm, or 1.2 * 10^-15 m 
where A = atomic number from A = 4 to A = 240
For Helium4, R = 1.9 fm
For Plutonium240 (half-life = 6580 years), R = 7.5 fm

A femtosecond (fs) is 10^-15 seconds (s).

Lightspeed is approximately 3 * 10^8 m/s
Light travels 3 * 10^-7 m in one fs.
A meter is approximately 39 inches.
Light travels approximately 1.2 * 10^-5 inches in one fs.

(I assume here that your laser normally produces visible light).

Visible light has a wave-length of approximately 1.2 * 10^-4 inches.
The diameter of a photon is 1/2 wavelength, or 6 * 10^-5 inches for
visible light.

In other words, the pulse of a femtosecond laser is approximately
1/5 or 20% the diameter of a photon of visible light.

Now consider the mechanics involved in generating a photon.
A photon is a quantum of electromagnetic energy.
An electron in motion induces a magnetic field.
An alternating current of electrons induces a fluxtuating magnetic field
of the same frequency. The magnetic field travels outwards (perpendicular
to the conductor) at the speed of light.
A full cycle of current is required to produce a full wavelength (2 photons)
of travelling magnetic energy.

There are three fundamental requirements which are common to all lasers
(and masers):

1: The medium has a pair of energy levels such that transitions between
   these levels causes emmission of radiation of a specific frequency.

2: The device resonates so that the photons of the desired frequency
   have enough time in the medium to induce many transitions.

3: Population inversion: the higher energy state needs to be more
   populated than the lower state so that emission is more likely
   to occur than absorption, that is, the radiation is amplified.

As mentioned above, the femtosecond pulse size being 10% of the
desired wavelength, I conclude that your device VIOLATES
requirement #2. (The device is cut off before a SINGLE transition
has had time to occur).
Therefore, your device is NOT a laser, by DEFINITION OF A LASER.
Therefore, your device will not be a coherent source of light.
Being a non-coherent source of light, your device will produce
a range of frequencies and polarizations. As you mentioned above,
the light that was measured by your device was wide spectrum.

Note that I reached this conclusion WITHOUT resorting to the
uncertainty principle! There are many other effects that can
be used to predict a wide spectrum from your device, such as
diffraction (at the boundaries of the lasing medium), harmonics
and interference from the induced ultraviolet photons (the
wavelength corresponding to the short pulse), hysteresis of the
circuitry and medium used, signal to noise ratio, and
non-linearity of the pulse itself (sorry, but it wont be a
square wave).

I would also conclude that a femto-second laser would be a valid device
if it was designed to operate with x or gamma ray frequencies.

> Nice try, though (keep it up!).

Cheers!

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