[Laser] Lasers vs LEDs & ARRL contests

[Glenn Thomas]

"Narrow bandwidth" is a relative term. Most unmodulated optical 
lasers have bandwidths that are a few gigahertz wide due to the 
Doppler shift of the individual photons caused by the random thermal 
motion of the molecule or atom doing the emitting. This is part of 
the reason why laser light doesn't stay coherent - if indeed it ever 
really was. ...and part of the reason why limiting optical 
communications for the purpose of Ham radio contests to allegedly 
coherent light is absurd at best.

73 de Glenn wb6w



At 05:31 PM 7/20/2008, GeoffK wrote:
>>By certain bandwidth I mean any light that most of it's output is 
>>confined to a narrow spectrum.  I guess this would apply to most 
>>any solid state light emitting device.
>>Dex
>I beg to differ: white-light sources, by definition, are broad 
>spectrum, with  many wavelengths across the visible spectrum - 
>perhaps even a continuous spectrum. Many Luxeons are white-light 
>output, and so are broad-spectrum/ non-coherent. There ARE 'single' 
>color Luxeons (and other LEDs) and I've never really understood why 
>some of the most narrow-spectrum units are not allowed (as long as 
>suitable 'narrow spectrum' language can be found).
>Modulation - I've always like simple OOK (on/off keying) which is 
>CW; you can't really do that with any source that requires higher 
>voltage, e.g. a gas tube like a HeNe, although it is easy with most 
>solid-state sources like laser diodes. There is nothing in the rules 
>that requires a particular form of modulation; just as long as the 
>required info is communicated any mod form is okay.
>Geoff WA2GFP
>
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