On the determination of χ(2) in thin films: a comparison of one-beam second-harmonic generation measurement methodologies

Abstract

The determination of the second-order susceptibility (χ(2)) of thin film samples can be a delicate matter since well-established χ(2) measurement methodologies such as the Maker fringe technique are best suited for nonlinear materials with large thicknesses typically ranging from tens of microns to several millimeters. Here we compare two different second-harmonic generation setups and the corresponding measurement methodologies that are especially advantageous for thin film χ(2) characterization. This exercise allows for cross-checking the χ(2) obtained for identical samples and identifying the main sources of error for the respective techniques. The development of photonic integrated circuits makes nonlinear thin films of particular interest, since they can be processed into long waveguides to create efficient nonlinear devices. The investigated samples are ABC-type nanolaminates, which were reported recently by two different research groups. However, the subsequent analysis can be useful for all researchers active in the field of thin film χ(2) characterization.

3D metamaterials

“…Again, as for negative-index metamaterials, losses inherited from metallic ingredients are responsible 83 . Purely dielectric 3D metamaterials 80,84,85 generally exhibit less-pronounced enhancements but might turn out to be more useful in practice 86 .…”

Formation of structural defects and strain in electrodegraded Fe‐doped SrTiO3 crystals due to oxygen vacancy migration

“…As a non‐destructive nonlinear technique, optical second harmonic generation (SHG) has been successfully utilized to study structural symmetry at perovskite‐type oxide surfaces, interfaces, and bulk regions . Most recently, our group used the optical SHG technique to characterize ionic defect and strain distributions across the electrodegraded interfaces and bulk regions of Fe‐doped SrTiO 3 (Fe:STO) single crystals .…”

“…As a non-destructive nonlinear technique, optical second harmonic generation (SHG) has been successfully utilized to study structural symmetry at perovskite-type oxide surfaces, interfaces, and bulk regions. [26][27][28][29][30][31][32][33] Most recently, our group used the optical SHG technique to characterize ionic defect and strain distributions across the electrodegraded interfaces and bulk regions of Fe-doped SrTiO 3 (Fe:STO) single crystals. 26,28,34,35 Electrostriction effects have been discussed based on our initial electric field-induced SHG measurements at the anode interfaces of reduced and oxidized Fe:STO single crystals.…”

Local structural changes due to the electric field‐induced migration of oxygen vacancies at Fe‐doped SrTiO3 interfaces

“…As a nondestructive nonlinear technique, optical second harmonic generation (SHG) has been successfully utilized to study structural symmetry at perovskite‐type oxide surfaces, interfaces, and bulk regions . Most recently, our group used the optical SHG technique to characterize ionic defect and strain distributions across the electrodegraded interfaces and bulk regions of Fe‐doped SrTiO 3 (Fe:STO) single crystals .…”