Quadrupole second-harmonic generation for a focused beam of arbitrary transverse structure and polarization

The theory of second-harmonic generation (SHG) that is due to quadrupole and magnetic-dipole second-order optical susceptibilities is developed for monochromatic, focused beams of arbitrary transverse mode structure and polarization character. The strength of SHG depends sensitively on the polarization character of the beam. © 1981 Optical Society of America.