Photocounts and laser detection of weak optical signals

The nature of photocounts arising in detectors exposed to highly coherent laser radiation is discussed. It is shown that the spatial localization of a photon allowed in quantum electrodynamics fails to account for the effect observed and that the Coulomb instability of a low electron flux in a photodetector can be the explanation. With detectors utilizing non-free electrons, namely, electrons bound in atoms, ions, molecules, etc., weak optical signals can be detected with laser radiation without photocounts, in other words, at a suppressed shot noise. A basic scheme for a laser detector using bound electrons is suggested.