Optical switching in organometallic phthalocyanine

Linear and nonlinear optical properties of human hemoglobin

In this study, we investigated the possibility of interactions between the solvent molecules with the Heme group in the human hemoglobin. The results of this study answer a key question: whether the interactions of the Heme unit with its surroundings are interdependent or independent of the protein units of human hemoglobin. Contributions of the intermolecular interactions were determined by exploiting the solvatochromism spectroscopic data by Kamlet-Taft (KAT) polarity functions. Solvent polarity effects on the nonlinear properties of the Heme's groups in the human hemoglobin (Hb) were investigated via the Z-scan method. The experimental results obtained with spectroscopic and nonlinear optical parameters (absorption coefficient and refractive index) show that the mechanism of solvation and the interactions of Heme are controlled by suitable configuration of the protein units of hemoglobin. In other words, interactions of the Heme with α- and β-globins are an effective factor in controlling the optical behavior of Heme.

Surfactant-dependant thermally induced nonlinear optical properties of l-ascorbic acid-stabilized colloidal GNPs and GNP-PVP thin films

Gold nanoparticle (GNP) colloids stabilized with various concentrations of l-ascorbic acid were synthesized by the chemical reduction method and characterized by UV-Vis spectroscopy, XRD, FT-IR spectroscopy and TEM. XRD and TEM studies confirmed the reduction in particle size with the stabilizer concentration. UV-Vis spectra showed a blue shift in the LSPR peak. FT-IR peaks ascertained the strong encapsulation of GNPs with l-ascorbic acid functional groups. The nonlinear optical (NLO) properties of colloidal GNPs and GNP-PVP composite thin film were investigated using the Z-scan technique with CW laser excitation at 632.8 nm. The effects of stabilizer concentrations on nonlinear refractive index (n 2), nonlinear absorption coefficient (β) and third-order susceptibility (χ (3)) of colloidal GNPs and GNP-PVP composite thin films were investigated. The values of the NLO parameters for the thin films were as large as n 2 = 10-5 cm2 W-1, β = 10-5 cm W-1 and χ (3) eff = 10-5 esu. For colloidal GNPs, these parameters were n 2 = 10-6 cm2 W-1, β = 10-6 cm W-1 and χ (3) eff = 10-7 esu. In both these cases, the NLO parameter values were found to decrease as the stabilizer concentration increased from 1 to 5 mM. The considerable enhancement in the NLO parameters may be attributed to the thermal lensing effect originating from the thermo-optic phenomenon. From the results, the influence of the concentration of the stabilizer on the NLO properties is obvious.

Influence of post-deposition annealing on structural, morphological and optical properties of copper (II) acetylacetonate thin films

In this study, the effect of thermal annealing under vacuum conditions on structural, morphological and optical properties of thermally evaporated copper (II) acetylacetonate, cu(acac)₂, thin films were investigated. The copper (II) acetylacetonate thin films were deposited using thermal evaporation technique at vacuum pressure ~1 × 10^-5 mbar. The deposited films were thermally annealed at 323, 373, 423, and 473 K for 2 h in vacuum. The thermogravimetric analysis of cu(acac)₂ powder indicated a thermal stability of cu(acac)₂ up to 423 K. The effects of thermal annealing on the structural properties of cu(acac)₂ were evaluated employing X-ray diffraction method and the analysis showed a polycrystalline nature of the as-deposited and annealed films with a preferred orientation in [1¯01] direction. Fourier transformation infrared (FTIR) technique was used to negate the decomposition of copper (II) acetylacetonate during preparation or/and annealing up to 423 K. The surface morphology of the prepared films was characterized by means of field emission scanning electron microscopy (FESEM). A significant enhancement of the morphological properties of cu(acac)₂ thin films was obtained till the annealing temperature reaches 423 K. The variation of optical constants that estimated from spectrophotometric measurements of the prepared thin films was investigated as a function of annealing temperature. The annealing process presented significantly impacted the nonlinear optical properties such as third-order optical susceptibility χ⁽³⁾ and nonlinear refractive index n₂ of cu(acac)₂ thin films.

Synthesis, characterization and third-order nonlinear optical properties of a dodecaruthenium organometallic dendrimer with a zinc(ii) tetraphenylporphyrin core

A new Zn(ii) porphyrin-based dendrimer (52) containing twelve Ru(ii) alkynyl fragments, has been prepared following a convergent approach in two steps from 5,10,15,20-tetra(4-ethynylphenyl)porphyrinatozinc(ii) (6). The cubic nonlinear optical (NLO) properties of 52 and other derivatives of 6 have been measured by third-harmonic generation (THG) at 1907 nm and by Z-scan over the spectral range 500-1700 nm, revealing the remarkable NLO response of 52 in the near-IR range. These results highlight the beneficial role of the extended "cross fourchée"-like polymetallic structure of 52 on its third-order NLO properties.

Fabrication and notable optical nonlinearities of ultrathin composite films derived from water-soluble Keggin-type polyoxometalates and water-insoluble phthalocyanine

Composite films with the general formula (POM/CuTAPc)_n derived from water-soluble Keggin-type polyoxometalates (POMs = H₅PMo₁₀V₂O₄₀, H₄SiW₁₂O₄₀, H₃PMo₁₂O₄₀ and H₃PW₁₂O₄₀) and water-insoluble 4,9,16,23-copper tetraaminophthalocyanine (denoted CuTAPc) are successfully fabricated by a layer-by-layer self-assembly technique and systematically characterized. The structure of the polyoxometalate anions in the multilayers is kept intact; the deposition amounts of POM and CuTAPc remain constant in every adsorption cycle of the composite film assembly process. The nonlinear optical properties of the composite films were studied by a Z-scan technique at a wavelength of 532 nm and a pulse width of 7 ns. The results not only show that the composite films exhibit notable optical nonlinear self-defocusing behavior and a saturated absorption effect with the nonlinear optical absorption co-efficient β, refractive index n₂, and third-order NLO susceptibility χ⁽³⁾ of the films increasing with the increase in number of layers of the films, but also reveal importantly that the discrepancy of LUMO levels between CuTAPc and POMs is proportional to their third-order NLO response.

Nonlinear optical response of platinum nanostructures and application for water detection in transformer oil

We report the fabrication of platinum nanostructures on an ITO substrate (Pt-NSs).

Nonlinear absorption in tetrathia[22]porphyrin(2.1.2.1)s: visualizing strong reverse saturable absorption at non-resonant excitation

meso-Substituted neutral, aromatic tetrathia[22]porphyrin(2.1.2.1)s represent a new entry in the family of nonlinear optically active porphyrins. The low fluence threshold values of these porphyrins endorse potential application as optical limiters.

Z-scan studies of the nonlinear optical properties of gold nanoparticles prepared by electron beam deposition

This paper details the fabrication process for placing single-layer gold (Au) nanoparticles on a planar substrate, and investigation of the resulting optical properties that can be exploited for nonlinear optics applications. Preparation of Au nanoparticles on the substrate involved electron beam deposition and subsequent thermal dewetting. The obtained thin films of Au had a variation in thicknesses related to the controllable deposition time during the electron beam deposition process. These samples were then subjected to thermal annealing at 600°C to produce a randomly distributed layer of Au nanoparticles. Observation from field-effect scanning electron microscope (FESEM) images indicated the size of Au nanoparticles ranges from ∼13 to ∼48  nm. Details of the optical properties related to peak absorption of localized surface plasmon resonance (LSPR) of the nanoparticle were revealed by use of UV-Vis spectroscopy. The Z-scan technique was used to measure the nonlinear effects on the fabricated Au nanoparticle layers where it strongly relates LSPR and nonlinear optical properties.

Optical, electrochemical, third order nonlinear optical, and excited state dynamics studies of bis(3,5-trifluoromethyl)phenyl-zinc phthalocyanine

Synthesis and characterisation of a Zn phthalocyanine substituted with bis(3,5-trifluoromethyl)phenyl groups at peripheral positions by absorption, fluorescence and electrochemical techniques. Excited state dynamics were investigated by fs degenerate pump–probe spectroscopy.

Enhanced reverse saturable absorption of electrostatic self-assembled layer by layer films containing (8-quinolineoxy-5-sulfonic acid)phthalocyanine cobalt and graphene oxide

The 25-bilayer CoPc/GO film was fabricated through electrostatic self-assembled layer by layer (LBL) technique, and it exhibits strong reverse saturable absorption (RSA) effect with the input intensity of 1.16 μJ.

Study of self-defocusing, reverse saturable absorption and photoluminescence in anthraquinone PMMA nanocomposite film

The nanocomposite film of 1,5-diamino-9,10-anthraquinone in poly methyl methacrylate has been fabricated by following guest-host method. Intense reverse saturable absorption and self-defocusing effect have been investigated by employing Z-scan technique with low power CW laser at 532 nm with different intensities for the dye-polymer composite film. The estimated values of nonlinear absorption coefficient β, nonlinear refractive index n2 and third order susceptibility χ((3)) of the composite film are of the order of 10(-3) (m/W), 10(-11) (m(2)/W) and 10(-4) (esu), respectively. The dye molecules have been encapsulated uniformly between molecules of polymer as a nanocomposite with average roughness ∼7.96 nm as characterized by AFM technique. The nanocomposite film also exhibited strong photoluminescence emission when excited with 532 nm. The second order hyperpolarizability of composite film has also been estimated. The evaluated figure of merit W having a value greater than 1, and the results obtained suggest that the composite film of 1,5-diamino-9,10-anthraquinone-PMMA has potential applications in nonlinear optical devices.

Investigation of synthesis, crystal structure and third-order NLO properties of a new stilbazolium derivative crystal: a promising material for nonlinear optical devices

A new organic stilbazolium derivative crystal 2-[2-(3-hydroxy-4-methoxy-phenyl)-vinyl]-1-methyl-pyridinium naphthalene-2-sulfonate dehydrate (C₂₅H₂₃NO₅S·2H₂O) (VSNS) was synthesized successfully.

The lifetime of the triplet excited state and modulation characteristics of all-optical switching in phenoxy-phthalocyanines liquid

We present our experimental results on the measurements of excited state dynamics in 2, 9, 16, 23-phenoxy-phthalocyanine (Pc1) and 2, 9, 16, 23-phenoxy-phthalocyanine-zinc (Pc2) using the pump-probe experiment. The results show that the lifetime of the first triplet excited state of the Pc2 longer than Pc1. The lifetimes of the triplet excited state for Pc2 and Pc1 are 12.8 μs and 10.1 μs at the same intensity, respectively. Moreover, analysis of modulation characteristics of all-optical switching (A-OS) shows that the stronger the light intensity of the pump light is, the smaller the normalized transmittance is, and the lower the A-OS response time is. The consequences of such short lifetimes are also discussed in view of the strong A-OS properties of these molecules.

Ultrafast third order nonlinear optical properties of water soluble zinc-octacarboxy-phthalocyanine

Synthesis and measurements of third order nonlinear optical (NLO) coefficients of water soluble zinc octacarboxy phthalocyanine (ZnOCPc) are reported here using different laser pulse durations. Nonlinear absorption and refraction behaviour in the nanosecond (ns), picosecond (ps) and femtosecond (fs) time domains were studied in detail. Three-photon absorption was the prevalent mechanism with femtosecond laser excitation whereas strong reverse saturable absorption due to dominant two-photon absorption (TPA) was observed with picosecond and nanosecond excitations. We have evaluated the sign and magnitude of the third order nonlinearity in fs, ps, and ns regimes. We observed large off-resonant second order hyperpolarizability (γ) with ultrafast nonlinear optical response in the femtosecond domain using degenerate four wave mixing (DFWM) technique. We also report the optical limiting characteristics and figure of merit (FOM) of ZnOCPc for optical switching.

Nonlinear optical properties of lutetium bisphthalocyanine and its application for an optical switch

The nonlinear optical (NLO) properties of lanthanide bisphthalocyanine (Lu(TBPc)Pc), including first hyperpolarizability, second hyperpolarizability and reverse saturable absorption (RSA), have been investigated. Furthermore, Lu(TBPc)Pc has also been applied for optical switch based on its RSA performance.

Studies of third-order optical nonlinearities and optical limiting of 2, 3-butanedione dihydrazone

2, 3-butanedione dihydrazone (BDDH) synthesized via chemical route and nonlinear optical parameters, such as nonlinear refractive index (n2), nonlinear absorption coefficient (β), third-order nonlinear optical susceptibility (χ(3)), second hyperpolarizability (γ), and optical-limiting behavior were investigated by single beam z-scan technique for different concentrations. Synthesized sample were irradiated by a Q-switched, frequency doubled Nd:YAG laser and found that n2 and β increases linearly with increasing concentration and hence γ decreases linearly. The excited-state absorption cross sections of BDDH were found to be larger than ground-state absorption cross sections, and it leads to reverse saturable absorption (RSA). The experimental results are well in agreement with the theory and also establish BDDH as one of the potential candidate materials for optical limiting at 532 nm.

Optical-Limiting and Photophysical Properties of Two Soluble Chloroindium Phthalocyanines with α- and β-Alkoxyl Substituents

Two soluble heavy-metal phthalocyanine derivatives, namely, tetra-alpha-(2-ethylbutoxy) chloroindium phthalocyanine (alpha-InPcCl) and tetra-beta-(2-ethylbutoxy) chloroindium phthalocyanine (beta-InPcCl), were synthesized. Their optical-limiting properties in THF solution were investigated with a 532 nm nanosecond laser. The differences in the optical-limiting properties are attributed to their different photophysical properties. alpha-InPcCl is superior to beta-InPcCl as optical-limiting material, alpha substitution could be a useful factor to be considered in designing optical limiting materials based on metal phthalocyanines.