We present measurements of fourth-harmonic generation in reflection from the interface between two centrosymmetric media [Si(001)– SiO<sub>2</sub>] , using femtosecond pulses well below damage threshold. Analyses of signal amplitudes, rotational anisotropy, and sensitivity to surface roughening reveal that the surface dipole fourth-harmonic contribution dominates the bulk quadrupole contribution much more strongly than for second-harmonic generation.
© 1998 Optical Society of America
Y.-S. Lee and M. C. Downer, "Reflected fourth-harmonic radiation from a centrosymmetric crystal," Opt. Lett. 23, 918-920 (1998)