Measurement of Fourth-Order Coherence Functions

In this paper we outline a method which allows one, in principle, to measure $〈E_i({\mathrm{x}}_1, t)E_j({\mathrm{x}}_2, t){E_k}^{*}({\mathrm{x}}_3, t)\times {E_l}^{*}({\mathrm{x}}_4, t)〉$ (in general, ${\mathbf{x}}_1$≠${\mathbf{x}}_2$≠${\mathbf{x}}_3$≠${\mathbf{x}}_4$), for stationary quasimonochromatic light propagating principally in the forward direction. The procedure makes use of the properties of nonlinear dielectrics in a sequence of interference experiments. No correlation of photoelectron currents is used, and as a special case the contracted moment $〈{\left|E_i\right({\mathrm{x}}_1, t\left)\right|}^2{\left|E_j\right({\mathrm{x}}_2, t\left)\right|}^2〉$ measured by Hanbury Brown and Twiss could be obtained in this manner. It is shown that it should be possible to measure the full fourth-order coherence function in the laboratory for laser light, using presently obtainable intensity levels.