Calibration of multipolar second-order response of isotropic bulk materials

The bulk response for second-harmonic generation (SHG) is best accessed in a geometry with two incident fundamental beams, which intersect in the sample. The finite overlap of the two beams and the resulting varying interaction strength along the beam propagation direction precludes reliable calibration of the multipolar nonlinearity using the traditional Maker fringe technique. In this paper, we present a novel technique that takes advantage of the two-beam geometry and allows absolute calibration of the multipolar response against a known reference material.