> This is why lasers are very popular for communications: a concentrated beam can deliver a very high signal-to-noise ratio. With LEDs, it's tougher because the beam is dispersed and you don't want to blind people with high power output
I suppose I am missing something obvious... but laser beams are shaped into a beam by way of a lens at the end of a tube, right? The laser diodes I've seen emit light in all directions. You could just as well stick an LED at the bottom of that tube.
Classic lasers directly emit coherent beam without the need for additional optics. Output aperture of most lasers might seem to emit light into all directions, but most of the output power is concentrated into the direction of the resonant cavity. Due to manufacturing tolerances low power laser diodes tend to produce somewhat irregular output beam (both diverging and uneven) which is then compensated for using some external optics that also serve to set required width of the final output beam.
It is impractical to convert light from some arbitrary "point-like" source (ie. LED) into beam that has low divergence by lenses or similar optics.
Lasers generate coherent radiation, the frequency of the light is much more monochromatic (set by the optical cavity) than a bare LED (set by the thermally smeared band gap of the material).
Even a very cheap laser diode can have the output collimated with a single lens, resulting in a beam that diverges a fraction of a percent. Hence cheap laser pointers.
Try and do the best you can with an LED and you will end up with a torch.
I suppose I am missing something obvious... but laser beams are shaped into a beam by way of a lens at the end of a tube, right? The laser diodes I've seen emit light in all directions. You could just as well stick an LED at the bottom of that tube.