"lu6etj" wrote news:0d91fd84-c798-4391-8e90-I do not
have useful knowledge in laser either.

I am interested in your optical analogy because analogies often are
useful to visualize a new thing knowing old things, it does not matter
if we use RF concepts to aproximate optical things or vice versa,
analogies are useful crutches (muletas in spanish). Even I agree at
our concept that electromagnetic spectrum includes RF waves and ligh
waves and they are the same phenomenon, I think that is a result of
great insight and efforts of the human mind, it is not so evident. We
see light, we sense infrared radiaton, but we can not perceive well RF
without instruments (unless we introduce ourselves in a micowave oven
or burn with the antenna, of course ).
To concentrate light we only need a piece of glass, to do the same on
HF RF region we need large wire antenna arrays. Because of this we
often need (or employ) very differents models to deal with the "same
thing". Probably Maxwell equations solve all of them, but they are
difficult ladies to deal :).

Maxwell equations are wrote by Heaviside.

Reconciling optcs models with electric models have its difficulties,
but can be productive undoubtedly I believe.

Now light is produced with the electric device:
"As the electrons are undergoing acceleration they radiate electromagnetic
energy in their flight direction, and as they interact with the light
already emitted, photons along its line are emitted in phase, resulting in a
"laser-like" monocromatic and coherent beam. The mirrors show in the sketch
below are superfluous, as all the light is emitted in one direction anyway."
From: http://en.wikipedia.org/wiki/Halbach_array

When electrons oscillate they disturb the "electron see" and that are waves.
To achive the oscillations we use different devices.
The Halbach array is for light. The dipole for RF. For radar and microwaves
the another.
S*