Third-order Nonlinear Optical Phenomena Research Articles

Large optical nonlinearity enhancement under electronic strong coupling

Nonlinear optical responses provide a powerful way to understand the microscopic interactions between laser fields and matter. They are critical for plenty of applications, such as in lasers, integrated photonic circuits, biosensing and medical tools. However, most materials exhibit weak optical nonlinearities or long response times when they interact with intense optical fields. Here, we strongly couple the exciton of cyanine dye J-aggregates to an optical mode of a Fabry-Perot (FP) cavity, and achieve an enhancement of the complex nonlinear refractive index by two orders of magnitude compared with that of the uncoupled condition. Moreover, the coupled system shows an ultrafast response of ~120 fs that we extract from optical cross-correlation measurements. The ultrafast and large enhancement of the optical nonlinar coefficients in this work paves the way for exploring strong coupling effects on various third-order nonlinear optical phenomena and for technological applications.

Second and third-order nonlinear optical behavior of natural pigment: chlorophyll and crocin

To provide an insight into the microscopic second and third-order nonlinear optical (NLO) behavior of chlorophyll a and crocin, we have computed the electric dipole moments (μ), dispersion-free first hyperpolarizabilities (β), frequency-dependent first and second (γ) hyperpolarizabilities at 1064 nm wavelength area using time-dependent Hartree-Fock (TDHF) method. According to ab-initio calculation results, the examined compounds exhibit first and second hyperpolarizabilities with non-zero values, implying second and third-order NLO phenomena.

Natural silk protein as a new broadband nonlinear optical material

Third-order nonlinear optical phenomena lie at the heart of all-optical signal processing, where laser pulses are used to switch, modulate, or gate another laser pulse. Here we report that the solidified silk film possesses extremely large third-order susceptibilities (~10−9 esu) in a wide near-infrared spectral region. The nonlinearity of silk protein can be substantially enhanced by inducing stronger molecular interactions from van der Waals forces and hydrogen bonding. The biocompatibility and capability of nanofabrication techniques will enable us to pave new ways for nonlinear bioimaging and biosensing applications.

Ab-initio and DFT methodologies for computing hyperpolarizabilities and susceptibilities of highly conjugated organic compounds for nonlinear optical applications

In this talk, after a short introduction on the methodologies used for computing dipole polarizability (α), second and third-order hyperpolarizability and susceptibility; the results of theoretical studies performed on density functional theory (DFT) and ab-initio quantum mechanical calculations of nonlinear optical (NLO) properties for a few selected organic compounds and polymers will be explained. The electric dipole moments (μ) and dispersion-free first hyperpolarizabilities (β) for a family of azo-azulenes and a styrylquinolinium dye have been determined by DFT at B3LYP level. To reveal the frequency-dependent NLO behavior, the dynamic α, second hyperpolarizabilities (γ), second (χ(2)) and third-order (χ(3)) susceptibilites have been evaluated using time-dependent HartreeFock (TDHF) procedure. To provide an insight into the third-order NLO phenomena of a series of pyrrolo-tetrathiafulvalene-based molecules and pushpull azobenzene polymers, two-photon absorption (TPA) characterizations have been also investigated by means of TDHF. All computed results of the examined compounds are compared with their previous experimental findings and the measured data for similar structures in the literature. The one-photon absorption (OPA) characterizations of the title molecules have been theoretically obtained by configuration interaction (CI) method. The highest occupied molecular orbitals (HOMO), the lowest unoccupied molecular orbitals (LUMO) and the HOMO–LUMO band gaps have been revealed by DFT at B3LYP level for azo-azulenes, styrylquinolinium dye, push–pull azobenzene polymers and by parametrization method 6 (PM6) for pyrrolo-tetrathiafulvalene-based molecules.

Nonlinear optical features on Yb3+/Tm3+ codoped PbO-GeO2 glasses with Si nanoparticles

Studies of third-order nonlinear optical phenomena on Yb3+/Tm3+ co-doped PbO-GeO2 glasses containing different concentration of silicon nanoparticles are presented. The well-known melting-quenching technique was used for the production of the samples. Measurements were performed using conventional Z-scan, SHG and ESHG methods with Q-switched mode-locked ns scale Nd-YAG lasers, intensities in the 0.8–1.2GW/cm2 power density range and repetition rate of 10Hz. Maximum third-order susceptibilities and second harmonic generation were found for the sample prepared with 1wt% of Si powder.

Enhanced third-order nonlinear effects in slow-light photonic-crystal slab waveguides of line-defect

We experimentally studied enhancement of the third-order nonlinear optical phenomena, i.e., self-phase modulation due to optical Kerr effect and two-photon absorption (TPA) in a small group-velocity (V(g)) line-defect guided-mode of AlGaAs-based photonic-crystal slab waveguide. We found that the phase shift Deltaphi or nominal Kerr constant n'(2) and TPA coefficient beta were strikingly enhanced due to small V(g) as the band edge was approached, such that they were proportional to (V(g))(-2); the nonlinear refractive index n(2) is enhanced proportional to V(g)(-1). We also observed that owing to this enhancement as well as an extremely small cross-section area, the energy required for inducing pi-phase shift was very small, being of an order of a few pJ for 5 ps optical pulse and for a 0.5-mm long sample. Based on those results, we discuss the possibility of developing ultra-fast and ultra-small all-optical switches that operate due to cross-phase modulation.

Structure, Spectroscopic Study and ab initio Calculations on Third-order Nonlinear Optical Behavior of N-(2-Hydroxy-4-methoxybenzylidene)-3- nitroaniline

Abstract N-(2-hydroxy-4-methoxybenzylidene)-3-nitroaniline (1) has been synthesized and characterized by X-ray diffraction analysis, FTIR and 1H NMR spectroscopy. The maximum one-photon absorption (OPA) wavelengths recorded by quantum mechanical computations using a configuration interaction (CI) method are estimated in the UV region to be shorter than 450 nm, showing good optical transparency to the visible light. We have computed both dispersion-free (static) and also frequency-dependent (dynamic) linear polarizabilities (α) and second hyperpolarizabilities (γ) by using the time-dependent Hartree-Fock (TDHF) method to provide an insight into the microscopic third-order nonlinear optical (NLO) behavior of the title compound. The ab initio calculation results with non-zero values on (hyper)polarizabilities indicate that the synthesized molecule might possess microscopic third-order NLO phenomena.

SYNTHESIS, CRYSTAL STRUCTURE, SPECTROSCOPIC STUDIES ANDAB-INITIOCALCULATIONS ON THIRD-ORDER OPTICAL NONLINEARITY OF A FIVE-COORDINATE CHLOROIRON(III) COMPLEX

A five-coordinate chloroiron(III) complex has been synthesized and characterized by X-ray diffraction analysis and UV-Vis spectroscopy. The maximum one-photon absorption (OPA) wavelengths recorded by both linear optical measurements and quantum mechanical computations using the configuration interaction (CI) method are estimated to be shorter than 400 nm in the UV region, showing good optical transparency to visible light. To investigate the microscopic third-order nonlinear optical (NLO) behavior of the title compound, we have computed both dispersion-free (static) and also frequency-dependent (dynamic) linear polarizabilities (α) and second hyperpolarizabilities (γ) at λ = 825–1125 nm and 1050–1600 nm wavelength areas using the time-dependent Hartree–Fock (TDHF) method. The ab-initio calculation results with non-zero values on (hyper)polarizabilities indicate that the synthesized molecule might possess microscopic third-order NLO phenomena.

Polydiacetylenes and analogies to inorganic semiconductors and graphite

The crystallography and one-dimensional electronic structure of polydiacetylenes (PDAs) stimulate a variety of chemical and physical studies. 13C CP-MAS n.m.r. studies of the PDAs from PTS and TCDU as well as 1, 1, 4,-4-tetraphenylbutatriene establish the en-yne bond representation for TCDU and rule out a significant contribution from a butatriene form to the ground state at room temperature. The current status of third-order non-linear optical phenomena in PDAs and the conversion of PDAs to conductive materials by ion implantation is presented. Our anisotropic chemical modification of poly-DCH is conceptually distinguished from the usual charge transfer doping of non-crystalline polymers.

Nonlinear refractive-index phenomena in isotropic media subjected to a dc electric field: Exact solutions

An exact, closed-form solution is presented for the propagation characteristics of an intense, arbitrarily polarized optical beam in an isotropic medium which is subjected to a dc electric field. The related phenomena of dc-electric-field-induced optical rectification and second-harmonic generation are examined as well as the propagation characteristics of a weak beam in an isotropic medium in the presence of both the intense optical and dc fields. One fundamental and noteworthy aspect of the results presented here is that both the formalism and the resulting solutions for these third-order nonlinear optical phenomena are given explicitly and entirely in terms of the set of real, observable Stokes parameters rather than in terms of the electric field amplitudes and phases.

Local field cascading in third-order non-linear optical phenomena of liquids

Contributions to the third-order non-linear polarization response of molecular liquids due to cascaded second-order processes are discussed. The cascading occurs entirely because of the presence of a reaction field to the second-order polarization of non-centrosymmetric molecules. Application of a simple dielectric continuum model is used to investigate relative magnitudes, polarization anisotropy and resonance behavior.