Second harmonic generation responses of KH₂PO₄: importance of K and breaking down of Kleinman symmetry

Abstract

The importance of K in the SHG responses and the breaking down of Kleinman symmetry were revealed in KDP.

A Series of Pentanary Salt-Inclusion Chalcogenoborates Containing a B12Q12 (Q = S, Se) Cluster Exhibiting a Kleinman-Forbidden Frequency-Doubling Effect

“…Therefore, it is better to combine Kleinman symmetry and Kramers–Kronig dispersion relations to interpret the experimental SHG activities . Besides, Deng’s work indicates that Kleinman symmetry is poorly obeyed for NLO-active materials with a lower symmetry, which was verified by the case of two polymorphs of KDP …”

“…53 Besides, Deng's work indicates that Kleinman symmetry is poorly obeyed for NLO-active materials with a lower symmetry, which was verified by the case of two polymorphs of KDP. 54 Theory Calculation. The band structure, density of states (DOS), and optical properties of The selenides exhibited more enhanced SHG effects than the sulfide, while they had a smaller birefringence.…”

The Microscopic Origin of Second Harmonic Generation Response: The Spatial Structure of Instantaneous Dipole Moments in Electron Excitation

“…The dipole moments are different from the dipole moments at � hω = 0, which are static without optical excitation and completely determined by the crystal structure. [29,30] In SHG calculations, the only wavefunction-involved quantity is the position matrix, which is calculated by using instantaneous Bloch eigenwavefunctions Y nk t ð Þ with the band index n and wavevector k. The transformation from Bloch eigenwavefunctions to atomic orbital wavefunctions j of a specific atom is…”

Electronic structures and optical spectra of KDP crystals with Sp doping defects: a first-principles study

“…Potassium dihydrogen phosphate (KH 2 PO 4 , KDP) has two structures including the paraelectric phase (PE) and the ferroelectric phase (FE). 1 The space groups of the two structures are I 4̄2 d and Fdd 2, respectively, where the KDP crystals of the FE phase are formed at temperatures below 123 K. 2 KDP crystals are wide band gap insulators. Experimentally, the band gaps of the PE and FE phases are 7.2 eV and 8.0 eV, respectively.…”