[General] Light from Light reflection

Sat Aug 15 09:50:16 PDT 2015

Hello All,

It was great meeting with all of you.  

I would like to introduce a different perspective to the discussion of the interaction of light with a thought experiment.  Suppose that we have a billion small microwave antennas randomly distributed in space.  The antennas on average are separated by a distance equal to about 10% of the wavelength that they will emit and the size of each antenna is much smaller than a wavelength.  A billion of these antennas from a “cloud” about 100 wavelengths in diameter.  If each antenna emits randomly, then the total cloud of antennas would emit an incoherent spherical emission pattern.  However, if all antennas emit the same frequency and if the phase is properly controlled, then the emitted radiation can form a beam with a divergence angle of about 0.01 radian.  Furthermore, the beam can be steered to propagate in any direction with proper phase adjustment.  When the emission forms a coherent beam, then the cloud of antennas feels momentum in the opposite direction of the emitted radiation. This momentum would accelerate the cloud of antennas in the recoil direction.

The example just given is a simulation of what happens in a laser.  Each atom in the excited state can either emit a photon by spontaneous emission or by stimulated emission.  When stimulated emission occurs, the emission is still generally spherical, but the phase of emission is coordinated so that part of the spherical emission is coherently added to the beam causing the stimulated emission. The spherical emission of a single atom “interacts” with the other waves to form a collimated beam propagating in a particular direction. The force imparted to the emitting atom is random if the emission is spontaneous or in a particular direction if it is stimulated.  

In my way of looking at this, this example satisfies a loose definition of interaction of light waves.  I assume that there might be a way of looking at this in which it can be argued that there was no interaction of waves, but this position will require stretching of definitions.  

John M.

From: General [mailto:general-bounces+john=macken.com at lists.natureoflightandparticles.org] On Behalf Of David Mathes
Sent: Friday, August 14, 2015 8:58 PM
To: Nature of Light and Particles - General Discussion <general at lists.natureoflightandparticles.org>; Andrew Meulenberg <mules333 at gmail.com>
Subject: Re: [General] Light from Light reflection

Andrew

One paper that might be of interest is:

 <http://arxiv.org/abs/1205.5897> arXiv:1205.5897 [ <http://arxiv.org/pdf/1205.5897> pdf]

Spin and Orbital Angular Momenta of Light Reflected from a Cone

 <http://arxiv.org/find/physics/1/au:+Mansuripur_M/0/1/0/all/0/1> Masud Mansuripur,  <http://arxiv.org/find/physics/1/au:+Zakharian_A/0/1/0/all/0/1> Armis R. Zakharian,  <http://arxiv.org/find/physics/1/au:+Wright_E/0/1/0/all/0/1> Ewan M. Wright

Another paper is:

Fearn 2012 [1212.4469] Radiation Reaction Force on a Particle <http://arxiv.org/abs/1212.4469> 

David

From: Andrew Meulenberg <mules333 at gmail.com <mailto:mules333 at gmail.com> >
To: Nature of Light and Particles - General Discussion <general at lists.natureoflightandparticles.org <mailto:general at lists.natureoflightandparticles.org> >; Andrew Meulenberg <mules333 at gmail.com <mailto:mules333 at gmail.com> > 
Sent: Friday, August 14, 2015 8:36 PM
Subject: Re: [General] Light from Light reflection

Forgot the paper.

On Fri, Aug 14, 2015 at 11:33 PM, Andrew Meulenberg <mules333 at gmail.com <mailto:mules333 at gmail.com> > wrote:

Gentlemen,

In discussions after Bob Hudgins' presentation on Wednesday, I realized that we had been too close to the problem (and solution) and did not recognize the information gap that existed within the community. The reference was with regards to the nature of light-light interaction. The paper by Dowling (attached) identifies the problem between the NIW school and the light-light interaction school.

It is necessary to emphasize and clarify some points.

1.	Dowling proposed that IDENTICAL waves interact. However, 
2.	he was unable to PROVE reflection, rather than transmission.
3.	Mathematically the results are identical.
4.	In Dowling's paper, he demonstrates that even identical components of colliding waves have this property.
5.	The difference of the colliding waves always is transmitted, not reflected.
6.	Therefore, when added to the identical portion (that is the reflected part), the sum becomes equivalent to a transmitted wave.
7.	The paper showed that the differences could be in:

1.	phase
2.	amplitude
3.	polarity
4.	change in frequency

Thus, while Chandra's NIW view is almost always correct, if based on numbers alone, there is a growing field (based on lasers), which proves that interaction of identical light goes beyond Dirac's statement that photons can only interact with themselves. With this new information, it is possible to view ordinary light from a different perspective. "Any identical portions of light beams can (and will) reflect from each other." 

An example of this can be demonstrated by an introductory-physics  device (Newton's cradle, https://en.wikipedia.org/wiki/Momentum#Conservation ). Only if equal numbers of balls are dropped simultaneously will there be reflection of the same number as the input. If unequal numbers are dropped simultaneously, then it would appear that the larger number of balls is transmitted thru the set of balls. No one would say that the balls travel thru the stationary balls. Momentum reflection is the obvious answer in this case - and in the case of light. 

Had Dowling remembered this demonstration, he would have been able to say with absolute authority that light can reflect from light. The appendix of our paper is a mathematical proof of the null-momentum point in the center of the 'dark' zone for equal waves. This is the wave equivalent of the equal-particle demonstration.

My task for the next conference may be to demonstrate how this reflection effect affects the photon structure within the electron.

Andrew

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