Second-harmonic generation and linear electro-optical coefficients of BN nanotubes

Abstract

A systematic ab initio study of the second-order nonlinear optical properties of BN nanotubes within density functional theory in the local density approximation has been performed. Highly accurate full-potential projector augmented-wave method was used. Specifically, the second-harmonic generation (χ (2) abc ) and linear electro-optical (r abc ) coefficients of a large number of the singlewalled zigzag, armchair and chiral BN nanotubes (BN-NT) as well as the double-walled zigzag (12,0)@(20,0) BN nanotube and the single-walled zigzag (12,0) BN-NT bundle have been calculated. Importantly, unlike carbon nanotubes, both the zigzag and chiral BN-NTs are found to exhibit large second-order nonlinear optical behavior with the χ (2) abc and r abc coefficients being up to thirty times larger than that of bulk BN in both zinc-blende and wurtzite structures, indicating that BN-NTs are promising materials for nonlinear optical and opto-electric applications. Though the interwall interaction in the double-walled BN-NTs is found to reduce the second-order nonlinear optical coefficients significantly, the interwall interaction in the single-walled BN-NT bundle has essentially no effect on the nonlinear optical properties. The prominant features in the spectra of χ (2) abc (−2ω, ω, ω) of the BN-NTs are successfully correlated with the features in the linear optical dielectric function ε(ω) in terms of single-photon and two-photon resonances.

Second harmonic generation inh-BN and MoS2monolayers: Role of electron-hole interaction

“…The IPA level of theory is the one usually employed in theoretical calculations of SHG. Results for the h-BN monolayer were previously obtained by Guo and Lin [16] and are in good agreement with our calculations (see also Table I). In the following we show how effects beyond the IPA-that is, the additional terms in Eq.…”

“…In Table I we report the value of the second optical susceptibility at ω = 0, χ (2) (ω → 0), extrapolated from the SHG behavior at small frequencies. Again, at the IPA level our result agrees with the one of Guo and Lin [16] within the error bar. Adding the effects beyond IPA modifies the χ (2) (ω → 0) value, and in particular within TDSHF we found a value smaller by about 10% than within IPA.…”

“…With few isolated exceptions [13][14][15], a large number of calculations of nonlinear optical properties, and specifically of SHG in 2D crystals [16][17][18], employ the independent-particle approximation (IPA), which is inadequate for low-dimensional systems, where it is expected that the strongly bound excitons significantly modify the SHG.…”

The electronic, optical and ferroelectric properties of BiFeO3 during polarization reversal: A first principle study

“…The optical properties were calculated based on the independent-particle approximation and the excitonic effects and the local-field corrections were neglected [33][34][35]. The imaginary part of the dielectric function due to direction interband transitions is given by the Fermi golden rule, i.e., [33] e 00…”

Molar Binding Energy of Zigzag and Armchair Single-Walled Boron Nitride Nanotubes

“…In zigzag BN nanotubes, radial deformations that give rise to transverse pressures decrease the gap from 5 to 2 eV, allowing for optical applications in the visible range [29]. Importantly, both the zigzag and armchair tubes are found [30] (see also [31]) to exhibit large second-order nonlinear optical behavior with the second-harmonic generation and linear electro-optical coefficients being up to 15-times larger than that of bulk BN in both denser zinc-blende and wurtzite structures. This indicates that BN nanotubes are promising materials for nonlinear optical and optoelectronic applications.…”