Investigation Of Nonlinear Optical Response Research Articles

Investigation of nonlinear optical response and all-optical switching/modulation in pyrromethene 567 based on spatial self-phase modulation

Investigation on the response of pyrromethene 567 samples under the influence of a high-intensity 532 nm laser is carried out. When an intense light beam is absorbed by a medium, the phase of the beam undergoes a modulation, which in turn produces an interference pattern. Herein, we report the thermo-optic coefficient and nonlinear refractive index n 2 for low concentration of pyrromethene 567. All-optical switching/modulation using single and multiple wavelengths based on spatial self-phase modulation has been achieved. The work reveals the potential application of pyrromethene 567 in photonic devices including optical modulators, optical switches, and similar devices.

The investigation of nonlinear optical response of chalcone and PMMA united thin films for photonic applications

In this investigation an organic nonlinear optical potential {(E)-3-(4-bromophenyl)-1-(thiophen-2yl) prop-2-en-1-one (TB)} chalcone blended poly(methyl methacrylate) (PMMA) composite thin film are deposited using spray pyrolysis method. The direct optical band gap was determined using UV–Vis spectral response and was found to be in the range of 3.217–3.026 eV as in accordance with concentration. Photoluminescence studies show that the material emits in the blue and red band regions, implying that the films perhaps used as blue and red LED. The third order nonlinear absorption coefficient (β) and the optical limiting (OL) threshold of the films are determined by Z-scan technique and found in the order of 10−4 cm/W and 103 J/cm2 respectively. The obtained outcomes of deposited thin films may reinforce the capable potential for optical limiting applications.

DFT investigation of nonlinear optical response of organic compound: acetylsalicylic acid

Abstract Nonlinear optical studies of organic compounds have been widely conducted because of its great scope in molecular engineering. In the present work, we have chosen an organic compound acetylsalicylic acid due to its non-centrosymmetric structure and presence of extended conjugated π-system. Nonlinear optical response of the probe system has been explored computationally by using density functional theory with B3LYP/6-311G++(d,p) basis set. To explore the nonlinear optical response, Mulliken charge analysis, Raman, UV–vis, nuclear magnetic resonance, molecular electrostatic potential analysis, polarizability, first order hyperpolarizability etc., have been applied for the probe molecule. Observed high value of dipole moment of optimized structure, charge transfer in the system, high Raman activity, and high value of polarizability, first order hyperpolarizability validate the strong candidature of acetylsalicylic acid to be used as a nonlinear optical active material in the future.

Control of ultrafast photocurrent in twisted bilayer graphene by circularly polarized few-cycle lasers

We perform nonperturbative calculations of light field induced current in twisted bilayer graphene (tBLG) irradiated by a circularly polarized (CP) few-cycle laser pulse. The strong-field electron dynamics is simulated within a single-particle picture by two complementary approaches, including the velocity-gauge density-matrix equation and the length-gauge time-dependent Schr\"odinger equation, which both combine a tight-binding model for describing tBLG electronic structures. The two theoretical approaches yield the same result in the context of studying the carrier-envelope phase (CEP) and laser intensity dependent photocurrent. We show that the measured current exhibits a sinusoidal dependence on CEP of CP driving fields, with the sine phase determined by the electrode orientation with respect to the tBLG lattices. Moreover, it has been proven that an important reversal of the photocurrent direction occurs as the driving optical field strength increases to the strong-field regime, which cannot appear in the monolayer or conventional AA- and AB-stacked bilayer graphene. Based on the analysis of the conduction band population, we successfully identify that such current direction reversal in tBLG mainly originates from the interference of multichannel electron transition among two conduction bands and four valence bands closest to the Fermi level. Our results may pave the way toward investigation of nonlinear optical response in layered materials, and might provide insight for the design of future ultrafast optoelectronic devices.