Origin of the Photoinduced Optical Second Harmonic Generation Arising in N-Phenyl Microcrystalline Films

Abstract

Photoinduced second-order nonlinear optical effects, particularly optical second harmonic generation (SHG) of N-phenyls with different numbers of aromatic rings deposited on glass substrates were studied. As a fundamental beam, a 5-ps pulsed Nd:YAG laser was used. Quantum chemical time-dependent density functional theory (TDDFT) simulations of the nonlinear optical properties were performed. The first-order hyperpolarizabilities of isolated molecules were calculated, under the influence of a polarized pumping beam, to evaluate the role played by the nanointerfaces separating the microcrystallites and the amorphous environment. Consideration was performed within a framework of steady-state Langevin order parameters for amorphous-like films. A strong dependence of the photoinduced SHG versus the number of aromatic rings determining the degree of film crystallinity was shown. A comparison of experimental data and theoretically evaluated results shows that for the photoinduced first-order nonlinear optical effect the dominant contribution is an amorphous-like structural component, unlike the transport properties, where the crucial role is played by the nanointerface region. This may reflect a specific feature of the multiphoton processes in such types of nanointerfaces because of nanoconfined effects.

Excited States from Time‐Dependent Density Functional Theory

“…Beyond the linear regime, there is also growing interest in second-and third-order response [139][140][141][142] in all these fields. In particular the field of non-linear optics has been heavily investigated [143][144][145], especially the phenomenon of two photon absorption [146,[146][147][148][149][150][151][152][153].…”

Probing real time gold nanostar formation process using two-photon scattering spectroscopy

“…(3) Due to the presence of multipod, the intense electromagnetic field located around the pods, which can help to increase the TPS intensity as we and other groups have observed very high SERS intensity in the presence of nano-star. (4) Another possibility for high TPS intensity is due to increase in nano-confined effect, which can enhance NLO properties as reported recently [32][33]. It is also interesting to note from Table 1 that b value for nanostar is much higher than even nanoflower, though the size of nanoflower is bigger than nanostar and also k max shifted slightly towards blue for nanostar than that of nanoflower.…”

Helical Superstructure and Charged Polarons Contributions to Optical Nonlinearity of 2-Methyl-4-nitroaniline Crystals Studied by Resonance Raman, Electron Paramagnetic Resonance, Circular Dichroism Spectroscopies, and Quantum Chemical Calculations

“…The efficient nonlinearity of the disordered MNA (at RT) crystal and the negative result of its electric conductivity agree with the finding that the disorder plays a positive role toward NLO properties and a negative role with respect to electrical conductivity. 61,62…”