Determination of the third-order correlation function by noncollinear two-beam third-harmonic generation

A method was developed for determination of the third-order correlation function G⁽³⁾(0, τ) on the basis of noncollinear two-beam generation of the third harmonic in a cell containing an atomic metal vapour. The advantages of the proposed method are its simplicity, validity in a wide range of wavelengths, and ability to reveal the asymmetry of an ultrashort pulse in one laser shot. A criterion of the reproducibility of the laser output pulses from one shot to the next was established. In the case of smooth laser pulses it is possible to select a convenient analytic model for the function G⁽³⁾(0, τ). The capabilities of the method are demonstrated by the application to a picosecond YAIO₃ : Nd³⁺ laser.