2-PORT HOMODYNING OF A COHERENT SIGNAL AND THE ESSENCE OF SHOT NOISE

The process of two-port homodyning is calculated for a coherent signal and the subtraction of the photocurrents is modelled by double-mode twophoton absorption until the stationary state is attained. This allows a simple physical interpretation and can be treated analytically for a coherent local oscillator field. In addition, it is shown how the excess noise of a chaotic local oscillator is balanced out. The shot-noise level is given by the square root of the local oscillator photon number. This follows explicitly for a vanishing signal but is also derived for a present signal field. © 1990 Taylor & Francis Ltd.