SPATIOTEMPORAL COHERENCE PROPERTIES OF ENTANGLED LIGHT-BEAMS GENERATED BY PARAMETRIC DOWN-CONVERSION

We investigate the amplitude and intensity spatiotemporal coherence an d the photon coincidence rates of far-field down-converted light resul ting from the interaction of a pump wave of finite spectral width with a nonlinear crystal of finite spatial width. We examine the interplay between energy and phase mismatches and their effects on the intrabea m and interbeam spatial and temporal coherence of the down-converted b eams. We show that the down-converted light is spatially incoherent in the second order, and that the signal-idler fourth-order coherence ex tends over finite entanglement angles. We also study the effect of the apertures through which the down-converted light is collected, when t hey are centered at phase-matched or misaligned directions.