Multipolar tensor analysis of second-order nonlinear optical response of surface and bulk of glass

Abstract

We use two-beam second-harmonic generation to perform a quantitative tensor analysis of the effective dipolar surface nonlinearity and the separable multipolar bulk nonlinearity for BK7 glass. The most straightforward, self-consistent interpretation of the results is obtained when the effective surface response is assumed to have approximate Kleinman symmetry and the bulk contribution is dominated by magnetic, rather than quadrupole, effects.

Direct observation of bulk second-harmonic generation inside a glass slide with tightly focused optical fields

“…In addition, as suggested recently, strong multipole interactions may bypass the noncentrosymmetry requirement and promote applications of new nonlinear materials [10,11]. Therefore, a thorough understanding of the physical mechanisms behind bulk SHG from bulk centrosymmetric materials is fundamental for many practical applications utilizing SHG [12].Various attempts have been made to characterize surface and bulk contributions to SHG [7,8,13,14]. For example, the SHG based on two noncollinear fundamental beams [7,8] has been widely used to study surface and bulk contributions in a quantitative way.…”

“…Dipolar SHG is allowed through a surface contribution arising at the interface between centrosymmetric materials where centrosymmetry is broken [1,2]. However, when higher-order multipole interactions [3,4], such as magnetic-dipole and electric-quadrupole interactions, are taken into account, SHG can occur even inside bulk centrosymmetric materials, which was observed in several experiments [5][6][7][8]. When SHG is used as a surface or interface probe, it is essential to separate bulk contributions from the measured SH signal and verify that such multipolar contributions are actually negligible [9].…”

“…Various attempts have been made to characterize surface and bulk contributions to SHG [7,8,13,14]. For example, the SHG based on two noncollinear fundamental beams [7,8] has been widely used to study surface and bulk contributions in a quantitative way.…”

“…For example, the SHG based on two noncollinear fundamental beams [7,8] has been widely used to study surface and bulk contributions in a quantitative way. However, up to now, the separation of surface and bulk contributions is still known to be a fundamental difficulty in the field of SHG from centrosymmetric materials.…”

“…However, up to now, the separation of surface and bulk contributions is still known to be a fundamental difficulty in the field of SHG from centrosymmetric materials. Since two-beam overlap in a spatial region is usually several millimeters long [8], the excitation field is not highly localized. Furthermore, as the SH signal is often too weak to detect when the interaction volume is deep inside the bulk material, the excitation region is often chosen to be near the surface in order to maximize signal intensity [15].…”