Femtosecond Optical Kerr Gate Research Articles

Measurements of the scattering coefficients of intralipid solutions by a femtosecond optical Kerr gate

An ultrafast optical Kerr gate (OKG) in femtosecond time scale was used to determine the scattering coefficients of intralipids, in which the BI2O3-B2O3-SiO2 oxide glass was employed as the Kerr medium. Because of the joint action of the time gate and a transient spatial gate that was induced in the Kerr materials by the gating beam, more precise scattering coefficients could be obtained. Our experimental results show that, for low turbid media, the scattering coefficients measured using the OKG method are similar to those measured using the collimated transmittance (CT) approach, while for highly turbid media, the results obtained using the OKG method are bigger than those using the CT approach.

Enhancement of the optical Kerr effect exhibited by an integrated configuration of silicon quantum dots and silver nanoparticles

We present nonlinear refractive results for three different systems produced by ion implantation: high purity silica substrates with silicon quantum dots (Si-QDs), silver nanoparticles (Ag-NPs), and one sample containing both. We used a femtosecond optical Kerr gate (OKG) with 80 fs pulses at 830 nm to investigate the magnitude and response time of their nonlinear response. The Ag-NPs samples were prepared implanting 2 MeV Ag2+ ions at different fluencies. A sample with 1×1017 ions/cm2 showed no discernible Kerr signal, while for one with 2.4×1017 ions/cm2 we measured |χ(3)|1111 = 5.1×10-11 esu. The Si-QDs sample required irradiation with 1.5 MeV Si2+ ions, at a 2.5×1017 ions/cm2 fluence in order that the OKG results for this sample yielded a similar |χ(3)|1111 value. The sample containing the Si-QDs was then irradiated by 1 MeV Ag2+ ions at a 4.44 × 1016 ions/cm2 fluence and thermally treated, for which afterward we measured |χ(3)|1111 = 1.7×10−10 esu. In all cases the response time was quasi-instantaneous. These results imply that the inclusion of Ag-NPs at low fluence, enhances the nonlinearity of the composite by a factor of around three, and that this is purely electronic in nature. Pump-probe results show that there is not any nonlinear absorption present. We estimate that the confinement effect of the Si-QDs in the sample plays an important role for the excitation of the Surface Plasmon Resonance (SPR) related to the Ag-NPs. A theoretical model that describes the modification of the third order nonlinearity is also presented.

Preparation, physicochemical and third order nonlinear optical properties of bis(tetrabutylammonium)bis(2‐thioxo‐1,3‐dithiole‐4,5‐dithiolato)mercurate(II)

AbstractBis(tetrabutylammonium)bis(2‐thioxo‐1,3‐dithiole‐4,5‐dithiolato)mercurate(II) was prepared and characterized by elemental analyses, electronic absorption, infrared and X‐ray powder diffraction spectroscopy. The specific heat of the crystal was measured to be 1878.2 J.mol–1K–1 at 300 K. The thermal decomposition process was investigated by means of thermogravimetric analysis and differential thermal analysis measurements in air together with infrared and X‐ray powder diffraction spectra. The third‐order nonlinear optical properties at 800 nm were measured by femtosecond optical Kerr gate technique by using CS2 as reference. The third‐order optical susceptibility of its acetone solution at the concentration of 9.27 × 10–4 M was obtained to be 2.53 × 10–14 esu. The second‐order hyperpolarizability was estimated to be 1.7 × 10–32 esu and the response time was about 226 fs. The third order nonlinear optical properties at 532 nm were investigated by using the Z‐scan technique with 20 ps. It exhibited self‐focusing effect and saturable absorption. The second molecular hyperpolarizability was estimated to be 8.4 × 10–32 esu. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

STUDY ON THIRD-ORDER OPTICAL NONLINEARITY OF BIS(TETRABUTYLAMMONIUM)-Hg(dmit)2 BY FEMTOSECOND OPTICAL KERR GATE TECHNIQUE

Bis(tetrabutylammonium)- Hg(dmit) 2 was synthesized and its sample solution's optical Kerr Effect (OKE) signal was measured by the femtosecond optical Kerr gate technique. With the concentration of 9.27 × 10-4 M, the sample solution's third-order optical susceptibility was obtained to be 2.53 × 10-14 esu by using the CS2 OKE signal as reference signal measured under identical conditions. The second-order hyperpolarizability for the bis(tetrabutylammonium)- Hg(dmit) 2 molecular was estimated to be 1.7 × 10-32 esu. Its response time was about 226 fs, which is believed to be the contribution from the delocalized electrons.

Large and Ultrafast Third-Order Nonlinear Optical Propertiesof Ge-S Based Chalcogenide Glasses

We report ultrafast third-order nonlinear optical (NLO) properties ofseveral chalcogenide glasses GeSx (x = 1.8, 2.0, 2.5)measured by femtosecond time-resolved optical Kerr gate technique at820 nm. The third-order nonlinear susceptibility of GeS1.8 glassis determined to be as large as 1.41×10−12 esu, which is themaximum value of the third order nonlinear susceptibility χ(3)for the three compositions investigated. The symmetric Gauss profiles ofoptical Kerr signals reveal the nature of ultrafast nonlinear responseof these samples, which are originated from the ultrafast polarizationof the electron clouds. By detailed microstructural analysis of theseglasses based on the chain-crossing model (CCM) and therandom-covalent-network model (RCNM), it can be concluded thatχ(3) value of GeSx glasses can be enhanced greatly by S–Scovalent bonds or S3Ge–GeS3 ethane-like units.

Femtosecond third-order optical nonlinearity of the GeS 2–Ga 2S 3–CdI 2 new chalcohalide glasses

New chalcohalide glasses from the GeS 2–Ga 2S 3–CdI 2 glassy system have been prepared using the well-established melt-quenching method and its glass-forming region was given in this paper. According to the comprehensive consideration of thermal properties, the glass with the composition 0.8GeS 2–0.1Ga 2S 3–0.1CdI 2 was estimated to be the optimum composition within the studied glassy system. And its nonlinear refractive index n 2 of this glassy sample was estimated to be 7.5×10 −15 cm 2/W according to femtosecond time-resolved optical Kerr gate (OKG) measurement technique. The full width at half-maximum of the third-order correlation signal was 155 fs. Widely transmittance window, good glass-forming ability, higher χ (3) and large electronic ultrafast OKG response make these glasses the potential applications in current photonic field such as ultra-fast all-optical switching devices.

Ultrafast third-order optical nonlinearity of several sandwich-type phthalocyaninato and porphyrinato europium complexes

The third-order optical nonlinearity of two sandwich-type phthalocyaninato and porphyrinato europium complexes, including double- and triple-deckers (Eu[Pc(OC5H11)8]2, Eu2(Pc)(TPP)2, Pc=phthalocyanine, TPP=5, 10, 15, 20- tetraphenylporphyrinate), was investigated by using the femtosecond time-resolved optical Kerr gate method at 830 nm wavelength. Their second-order hyperpolarizability is estimated to be 0.74?10?30esu and 3.0?10?30esu respectively. This exhibits an evident enhancement in comparison with 0.47?10?30esu for one-decker Eu(Pc)(acac) (acac=acetylacetonate), which is also measured under the same conditions. The enhancement is attributed to the introduction of lanthanide metal to the large ?-conjugated system, intermacrocycle interaction and two-photon resonance etc.

Study on the third-order nonlinear optical properties of bis(tetraethylammonium)bis(1,3-dithiole-2-thione-4,5-dithiolato)mercury

A dmit2− salt: bis(tetraethylammonium)bis(1,3-dithiole-2-thione-4,5-dithiolato) mercury (EMDT) was synthesized. The optical Kerr effect (OKE) signal of its acetone solution was measured by the femtosecond optical Kerr gate technique. Using the CS2 OKE signal as a reference signal measured under identical conditions, the third-order optical nonlinear susceptibility, χ(3), of the sample solution was obtained as about 6.193 × 10−14 esu at the concentration of 1.39 × 10−4 M. The second hyperpolarizability for molecular EMDT was estimated to be as large as 2.73 × 10−31 esu. Its response time was about 184 fs, which is believed to be the contribution from the delocalized electrons.

OPTICAL NONLINEARITY OF Au METAL NANOPARTICLE DISPERSED (Ba,Sr)TiO3 THIN FILMS

Nearly spherical Au nanoparticles of about 3.83 nm diameter were embedded into the ( Ba , Sr ) TiO 3 matrix using alternating sputtering method, showing the characteristic surface plasmon resonance absorption band at 571 nm. Dispersion in the third-order optical nonlinearity was investigated at several wavelengths from 450 to 680 nm around the resonance peak by a single beam Z-scan technique with a wavelength tunable picosecond laser system. The real and imaginary parts of third-order nonlinear susceptibility were resolved and the relative contributions are quantitatively compared at each wavelength. The maximum absolute value of third-order susceptibility as large as 4.312 × 10-8 esu was obtained at the surface plasmon frequency. The temporal response was also characterized by the femtosecond time-resolved optical Kerr gate measurement and the nonlinear response time was evaluated to be 192 fs at the laser wavelength of 800 nm.

Study on the third-order nonlinear optical properties of bis(tetrabutylammonium)bis(1,3-dithiole-2-thione-4,5-dithiolato)cadium

A dmit2− salt: bis(tetrabutylammonium)bis(1,3-dithiole-2-thione-4,5-dithiolato) cadium (BCDT) was synthesized. The Optical Kerr Effect (OKE) signal of its acetone solution was measured by femtosecond optical Kerr gate technique. Using CS2 OKE signal as reference signal measured under identical conditions, the third-order optical nonlinear susceptibility, χ(3), of the sample solution was obtained to be about 1.08×10−13 esu at the concentration of 3.4×10−4 M. The second-order hyperpolarizability for BCDT molecular was estimated to be as large as 1.9×10−31 esu. Its response time was about 239 fs, which is believed to be the contribution from the delocalized electrons.

Laser irradiation induced enhancement on the ultrafast third-order optical nonlinearity of chalcogenide glass

The third-order optical nonlinearity of chalcogenide glass was investigated with the femtosecond optical Kerr gate system. With the long durative irradiation of the laser field, the ultrafast optical Kerr signal was observed to increase continuously till saturation. It was also found that this enhancement is anisotropic with respect to the laser polarization. Based on the intimate valence alteration pairs (IVAP) model, we explained this enhancement in terms of the light-induced orientation of valence alteration pairs.

Large and ultrafast third-order optical nonlinearity of GeS 2–Ga 2S 3–CdS chalcogenide glass

We report measurements of third-order optical nonlinearity of the 90GeS 2–5Ga 2S 3–5CdS (in mol%) chalcogenide glass using the femtosecond time-resolved optical Kerr gate technique at 820 nm. The third-order nonlinear susceptibility was estimated to be as large as 1.0 × 10 −12 esu. The full width at half maximum of the Kerr signal was 150 fs, implying that the sample had a response faster than 120 fs. Its response was dominantly assigned to the ultrafast distortion of the electron cloud. This glass sample is promising in future all-optical switching devices.

Near-infrared nonlinear properties of a glass–ceramic containing sodium niobate nanocrystals

We have investigated the third-order nonlinear optical response of a niobic–silicate glass–ceramic containing sodium niobate (NaNbO3) nanocrystals using picosecond Z-scan and femtosecond optical Kerr gate techniques at 1064 and 800 nm, respectively. The results show a large dependence of the nonlinear refractive index (n2) on the volume fraction occupied by NaNbO3 crystallites. Nonlinear absorption is negligible for all samples and the response time of the nonlinearity was shorter than 100 fs demonstrating that this material is a promising candidate for ultrafast optical switching.

Large and ultrafast third-order optical nonlinearity of heteroleptic triple-decker (phthalocyaninato)(porphyrinato)Sm(III) complexes

The third-order optical nonlinearity of two triple-decker mixed phthalocyaninato and porphyrinato Sm complexes, Sm 2(Pc) 2(TPP) and Sm 2(Pc)(TPP) 2 (Pc=phthalocyanine; TPP=5,10,15,20-tetraphenylporphyrinate), is investigated using the femtosecond time-resolved optical Kerr gate method at 830 nm wavelength. Their second-order hyperpolarizabilities are estimated to be 2.6 × 10 −30 and 2.2 × 10 −30 esu, respectively. Introducing of Lanthanide Sm to the large π-conjugated system, intermacrocycle interaction and two-photon resonance are considered responsible for the large optical nonlinearity.

Investigation on ultrafast third-order optical nonlinearity of metal(dmit) 2 /(mnt) 2 charge transfer complexes

We have investigated the transient third-order optical nonlinearity of the solutions of Metal(dmit)2/(mnt)2 salts in acetone by employing femtosecond optical Kerr gate measurement at 830 nm wavelength. An order of enhancement on the second-order hyperpolarizability is found for the above salts with central atoms of Cu and Ni. We have suggested an explanation for the enhancement based on the extension of electronic conjugation by the centring Cu or Ni atom.

Enhanced third-order nonlinear optical properties of C60–silane compounds

The nonlinear optical properties of C60[NH2–(CH2)3–Si(OC2H5)3]3 sol and gel were investigated by femtosecond optical Kerr gate technique at 820 nm. The nonresonant third-order optical susceptibilities were measured to be 1.4×10−13 and 1.6×10−13 esu for the C60[NH2–(CH2)3–Si(OC2H5)3]3 sol and gel, respectively, which are two orders larger than that of C60 molecule.

Dispersion study on third-order nonlinear optical properties of organic species with nitronyl nitroxide radical

The third-order nonlinearity of five stable organic radical species with nitronyl nitroxide group was investigated using a femtosecond optical Kerr gate method. The magnitudes of their second hyperpolarizability were measured at around 10- 34 -10-32 esu. The influence of the subtle chemical change of the molecular structure was explored. The experimental results were compared with theoretical calculation.

Investigation of third-order nonlinearity of an azo dye and its metal-substituted compounds

The real part of third-order optical nonlinearity of an azo dye (2-(2-thiazolylazo)-5-diethylaminophenol, TAEP) and those of its copper- and cobalt-substituted compounds are measured by using femtosecond optical heterodyne optical Kerr gate technique at the wavelength of 647 nm. All the values are found to be negative. Those of Cu- and Co-substituted compounds are found to be larger than that of the metal-free dye by two and three orders of magnitude, respectively. A negative γ eff as large as 10 −29 esu is found in Co complex. We use a three-level model to characterize the nonlinear process, and suggest that π-electron delocalization in metal complex leads to an enhancement.

Ultrafast third-order non-linear optical response of Diels–Alder adduct of fullerene C 60 with a metallophthalocyanine

The third-order optical non-linearity of a Diels–Alder adduct of fullerene C 60 with a copper phthalocyanine was investigated using the femtosecond time-resolved optical Kerr gate method at 830 nm wavelength. Its non-resonant second-order hyperpolarizability was estimated to be 5.4×10 −31 esu. The non-linearity enhancement from the formation of the intramolecular charge-transfer complex is discussed.

Two-photon resonance enhanced nonlinear optical response in C 60-copolymer charge transfer complex

Ultrafast third-order nonlinearity of C 60-poly tetrahydrofurfuryl methacrylate charge transfer complex was measured using femtosecond optical Kerr gate at both 640 nm and 820 nm wavelength. In the material's two-photon absorption region, extra large third-order nonlinear optical response was observed.