Electrically Controlled Auto Darkening Lenses: Mirrored or Transparent?

[Longknife]

The technology of electrically controlled auto darkening welding lenses wherein the lens protects the welders eyes by transforming from clear to opaque within milliseconds is fascinating. I would ask, is anyone aware of a lens that is electrically controlled but produces a mirrored surface?

With gas tube laser technology the beam is produced by firing electrons into the chamber which build up in energy by reflecting back and forth between the mirrored surfaces until such time as the beam is powerful enough to escape through the less reflective surface.

There seems to be a major loss of beam energy simply from having to overcome the mirrored surface in order to exit the excitation chamber. If one were able to use an electrically controlled surface of selectivity that would respond to a drop in electrical charge and go transparent, would the system not prove more efficient?

 

[Drakkith]

There seems to be a major loss of beam energy simply from having to overcome the mirrored surface in order to exit the excitation chamber.

There is very little loss in energy. The beam doesn't build up until it reaches some threshold before 'overcoming' the mirror, the mirror simply allows a percentage of all light through. Eventually an equilibrium is reached where as much energy is leaving the laser as is being pumped in.