The reference and signal beam would then be used to excite the electrons from the shallow traps back to the deep traps.

For example, in the case of a hologram, illuminating the grating with just the reference beam causes the reconstruction of the original signal beam.

The flower-like adornment atop her hat acts as a signal beam, but it apparently only works when in her robotic form.

High gain antenna may be of many designs, but all allow transmitting a narrow signal beam over greater distance than a non-directional antenna, often nulling out nearby interference sources.

You may be failing to pick up the love signals beamed your way from someone you see as just an acquaintance.