Method of Spatial Alignment of Focal Planes and Sample Positioning in the Pump–Probe Scheme

A new method is proposed for determining the mutual position of the focal planes of focusing elements and their spatial alignment along the laser beam propagation axis in the optical pump–probe scheme. The method is based on the effect of nonlinear absorption arising from the interaction of femtosecond laser pulses with matter. The practical application of this method is demonstrated using the example of setting up an optical scheme for measuring the temporal shape of a terahertz pulse with the electro-optical gating method.