Quadrupole second harmonic generation and sum-frequency generation in ZnO quantum dots

Abstract

The second harmonic generation (SHG) and the sum frequency generation (SFG) processes are investigated in the conduction band states of the singly charged ZnO quantum dot (QD) embedded in the HfO 2 , and the AlN matrices. With two optical fields of frequency ω p and ω q incident on the dot, we study the variation with frequency of the second order nonlinear polarization resulting in SHG and SFG, through the electric dipole and the electric quadrupole interactions of the pump fields with the electron in the dot. We obtain enhanced value of the second order nonlinear susceptibility in the dot compared to the bulk. The effective mass approximation with the finite confining barrier is used for obtaining the energy and wavefunctions of the quantized confined states of the electron in the conduction band of the dot. Our results show that both the SHG and SFG processes depend on the dot size, the surrounding matrix and the polarization states of the pump beams. C 2015 Author(s). All article content, except where otherwise noted, is licensed under a Creative Commons Attribution 3.0 Unported License. [http://dx

Third harmonic and sum-frequency generation in ZnO quantum dots

“…After obtaining the required energy levels and the wave functions [21,26], we calculate the third order nonlinear susceptibility coefficient leading to THG and SFG. The different material parameters used in our calculation are given in the Table 1.…”

“…The confinement potential V conf ðrÞ ¼ 0 [21,22], where e in and e out are the dielectric constant of the dot material and the matrix material, e is the electronic charge and e 0 is the permittivity of free space. For a wurtzite ZnO QD the total polarization P tot consists of the sum of the spontaneous polarization P SP (polarization at zero strain) and the strain induced piezoelectric polarization P PZ .…”

“…In the literature several studies have been reported on the nonlinear susceptibility in nanostructures [8][9][10][11][12][13][14][15][16][17][18][19][20][21]. The third order nonlinear processes offer an opportunity to extend the coherent light sources to shorter wavelengths which is advantageous for the operation of the optoelectronic devices at shorter wavelengths.…”

Determining nonlinear optical coefficients of metals by multiple angle of incidence heterodyne-detected sum-frequency generation spectroscopy

“…In the literature, the comparison between surface and bulk terms has been extensively studied for SHG, 49,50 but less so for SFG. 4,[51][52][53][54][55][56][57] There are two ways to describe the bulk contributions from an isotropic medium. The first one is inspired from the original work of Bloembergen and Pershan, 29 separating the nonlinear polarization inside the bulk into components parallel and perpendicular to the source wavevector q vis + q IR .…”

Selective Probing of Thin-Film Interfaces Using Internal Reflection Sum-Frequency Spectroscopy

“…as has been demonstrated in several experiments. [52][53][54][55][56][57][58] Selectively probing the interface at z = d necessitates the visible and infrared beams traversing the polymer film, so quadrupolar contributions may be significant. However, in cases where measurements of sufficiently thick films is possible in both internal and external reflection geometries, the spectra may be compared to those obtained for thin films.…”