Optical Kerr Gate Technique Research Articles

Near-infrared ultrafast third-order nonlinear optical response of 2D NbS2, NbSe2, ZrTe2, and MoS2.

By employing the optical Kerr gate technique at 800 nm with 180 fs pulses at 76 MHz, we evaluated the third-order nonlinear optical response of two-dimensional (2D) semiconducting MoS2, semimetallic ZrTe2, and metallic NbS2 and NbSe2. The modulus of the nonlinear refractive index was measured to range from 8.6 × 10-19 m2/W to 5.3 × 10-18 m2/W, with all materials' response time limited by the pulse duration. The physical mechanism to explain the ultrafast response time's origin considers the nature of the 2D material, as will be discussed.

Dynamic compressibility and third-order optical nonlinearities in carbon/metal-based nanofluids.

The influence of the superposition of two high-irradiance optical beams on the mechanical properties exhibited by carbon nanotubes decorated with platinum nanoparticles was analyzed. The change in density, compressibility modulus and acoustic velocity in the samples suspended in acetone and ethanol was estimated by measuring the nonlinear refractive index tested by a two-wave mixing experiment. The nanotubes were prepared by a spray pyrolysis processing route and the metal decoration was carried by chemical vapor deposition. High-Resolution Transmission Electron Microscopy studies confirmed the multiwall nature of the carbon nanotubes; while energy-dispersive X-ray spectroscopy reveals the separated presence of platinum nanoparticles incorporated to the hybrid nanostructures. An Nd-YAG laser system emitting at 532 nm wavelength with 4 ns pulse duration was used for conducting the third-order nonlinear optical evaluations by a standard optical Kerr gate technique. Comparative experiments showed that the composition of the liquid solution plays an important role in the manipulation of the density exhibited by the nanofluids. Remarkably, the incorporation of Pt in the tubes originates stronger changes of the mechanical characteristics induced by optical nonlinearities in the nanofluids irradiated by nanosecond pulses. Within this work, it is highlighted that potential applications for developing multivalent logic operations by fuzzy mechano-optic effects exhibited by nanofluids can be contemplated.

Ultrafast nonlinear optical properties and optical Kerr effect of In-doped ZnO nanowires

In-doped ZnO (IZO) nanowires were prepared using the chemical vapour deposition method. The nonlinear optical characteristic and optical Kerr transmittance of the IZO nanowires were studied by Z-scan and time resolved optical Kerr gate technique, respectively. Two and three-photon absorption coefficient of the samples were experimental obtained. Moreover, with an 800nm femtosecond excitation, an important Kerr signal originated by an induced birefringence was observed. These studies promise their potential applications in multifunctional all-optical devices.

Collective optical Kerr effect exhibited by an integrated configuration of silicon quantum dots and gold nanoparticles embedded in ion-implanted silica

The study of the third-order optical nonlinear response exhibited by a composite containing gold nanoparticles and silicon quantum dots nucleated by ion implantation in a high-purity silica matrix is presented. The nanocomposites were explored as an integrated configuration containing two different ion-implanted distributions. The time-resolved optical Kerr gate and z-scan techniques were conducted using 80 fs pulses at a 825 nm wavelength; while the nanosecond response was investigated by a vectorial two-wave mixing method at 532 nm with 1 ns pulses. An ultrafast purely electronic nonlinearity was associated to the optical Kerr effect for the femtosecond experiments, while a thermal effect was identified as the main mechanism responsible for the nonlinear optical refraction induced by nanosecond pulses. Comparative experimental tests for examining the contribution of the Au and Si distributions to the total third-order optical response were carried out. We consider that the additional defects generated by consecutive ion irradiations in the preparation of ion-implanted samples do not notably modify the off-resonance electronic optical nonlinearities; but they do result in an important change for near-resonant nanosecond third-order optical phenomena exhibited by the closely spaced nanoparticle distributions.

Efficient optical Kerr gating property of fluorotellurite glass

We investigated the ultrafast optical Kerr effect of the fluorotellurite glass (Ft glass), the nonlinear response time of which was measured to be less than 230fs, while the nonlinear refractive index was estimated to be 9.62×10−16cm2/W. Using optical Kerr gate (OKG) technique with Ft glass as Kerr medium, we obtained narrow-bandwidth and symmetric gated spectra from a supercontinuum (SC) generated by a femtosecond laser. Experimental results indicated that Ft glass was a good candidate for an OKG medium due to its fast response time, large nonlinearity, and high transparency.

Study on the Third-order Nonlinear Optical Properties of bis(tetraethylammonium) bis(1,3-dithiole-2-thione-4,5-dithiolato)cadium

A dmit2- salt: bis(tetraethylammonium)bis(1,3-dithiole-2-thione-4,5-dithiolato)cadium (CADMIT) was synthesized. The Optical Kerr Effect (OKE) signal of its acetonitrile 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, c(3), of the sample solution was obtained to be about 2.98 x 10-14 esu at the concentration of 1.57 x 10-3 M. The second-order hyperpolarizability of its molecular was estimated to be as large as 1.23 x 10-32 esu. Its response time was about 195 fs, which is believed to be the contribution from the delocalized electrons.

Application of Optical Kerr Gate with SrTiO3 Crystal in Acquisition of Gated Spectra from a Supercontinuum

We investigate the optical Kerr effect of SrTiO3 (STO) crystal, of which the nonlinear response time was measured to be less than 200 fs, while the nonlinear refractive index is estimated to be 2.16 × 10−15 cm2/W. Using the optical Kerr gate (OKG) technique with an STO crystal as the Kerr medium, we obtain narrow-bandwidth and symmetric gated spectra from a supercontinuum generated in distilled water by a femtosecond laser. The experimental results show superiority compared with the gated spectra obtained using OKG with CS2 as the Kerr medium, demonstrating that STO crystal is a promising OKG medium.

Third-order nonlinear optical response in transparent solids using ultrashort laser pulses

The third-order optical nonlinearity, χ (3), is measured in transparent glasses (BK7 and fused silica) and crystals (BaF2 and quartz) using 36-fs, 800-nm laser pulses and the optical Kerr gate (OKE) technique; values are found to lie in the range 1.3–1.7×10-14 esu, in accordance with theoretical estimates. We probe the purely electronic response to the incident ultrashort laser pulse in fused silica and BK7 glass. In BaF2 and quartz, apart from the electronic response we also observe contribution from the nuclear response to the incident ultrashort pulses. We observe oscillatory modulations that persist for ∼400 fs. The response of the media (glasses and crystals) to ultrashort pulses is also measured using two-beam self-diffraction; the diffraction efficiency in the first-order grating is measured to be in the range of 0.06–0.13 %. Third harmonic generation due to self-phase matching in the transient grating geometry is measured as a function of temporal delay between the two incident ultrashort pulses, yielding the autocorrelation signal.

Ultrafast third-order nonlinear optical properties of graphene in aqueous solution and polyvinyl alcohol film

The ultrafast third-order nonlinear optical properties of graphene in both suspension and film status are studied using femtosecond time resolved optical Kerr gate technique at 800nm. The third-order nonlinear optical susceptibility is 4.2×10−14esu for solution of 0.010mg/ml. The corresponding second-order hyperpolarizability is 3.4×10−32esu per carbon atom in graphene, which is the largest among the carbon family. The graphene embed in the polymer matrix of polyvinyl alcohol film (OD=0.43) exhibits strong ultrafast nonlinear optical response of 3.3×10−12esu and shows its potential application in nonlinear optics.

Nonlinear optical study of palladium Schiff base complex using femtosecond differential optical Kerr gate and Z-scan techniques

A femtosecond differential optical Kerr gate (DOKG) and Z-scan techniques, have been applied to investigate the third-order optical nonlinearity of composite film of the coordination complex [PdLPPh 3] (L=N-(2-pyridyl)-N′-(salicylidene)hydrazine, PPh 3=triphenylphosphine). Film exhibits superior nonlinear optical properties in the near-infrared spectral region. The nonlinear response time and third-order nonlinear optical susceptibility of complex were found to be≤90 fs and 3.9×10 −10 esu, respectively. The Z-scan result shows that saturable absorption property of the film and its nonlinear absorption coefficient of the sample was found to be −23 cm/GW.

Third-order nonlinear optical properties of C<sub>60</sub>-doped bulk material and its application in ultrafast optical Kerr gate

The ultrafast third-order nonlinear optical properties of C60+ vinyltriethoxysilane H2C=CHSi(OC2H5)3 (C60+VTES) sol-gel were investigated by the femtosecond optical Kerr gate (OKG) technique at 800 nm. The third-order optical susceptibility was measured to be 5.42 × 10−14 esu for C60+VTES at a weight concentration of 0.06 wt.%. Using C60+VTES as the OKG material, we acquired a series of narrow bandwidth and symmetric gated spectra continuously from the chirped white light continuum generated in water with femtosecond laser pulses. The gated spectra obtained using the C60+VTES OKG have distinct superiorities compared with CS2.

Enhanced ultrafast optical nonlinearity of porous anodized aluminum oxide nanostructures

Enhanced ultrafast optical nonlinearities of porous anodized aluminum oxide (AAO) nanostructures, well-known templates for quantum dots fabrication, have been investigated using the differential optical Kerr gate technique at 800 nm. The optical nonlinearity is strongly influenced by the pore number density, the pore size and the shape. Large values of the third-order nonlinear optical susceptibility (chi((3))) of the order of 10(-10)esu are measured. The nonlinear response time is faster than or comparable to the laser pulse width (90 fs) used. The origin and variation of such remarkable optical nonlinearities has been discussed by considering the nanoporous AAO as an effective medium and utilizing the extended Maxwell Garnet theory, and by considering the additional influence from pore diameter, pore shape and surface states.

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)

Bundling influence on ultrafast optical nonlinearities of single-walled carbon nanotubes in suspension and composite film

Nonlinear optical characteristics of single-walled carbon nanotubes (SWCNTs) dispersed in dichlorobenzene and imbedded in polymer were investigated at 800 nm using the time-resolved optical Kerr gate technique. For systematic study of the influence of SWCNT bundling on optical nonlinearities, SWCNT solutions with different concentrations and a series of SWCNT/polymer composites deposited on glass substrates with different concentrations and thicknesses were prepared. The nonlinear response was comparable to the pulse duration of the laser used (∼90 fs) both in SWCNT solutions and SWCNT/polymer composites. Over three orders of magnitude enhancement was observed in the third-order nonlinear susceptibility of SWCNT/polymer composite film compared with that of SWCNT solution. An appreciable reduction of microscopic and macroscopic nonlinearities was observed with increasing SWCNT concentrations due to stronger bundling of SWCNTs.

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.

SbS 3 enhanced ultrafast third-order optical nonlinearities of Ge–S chalcogenide glasses at 820 nm

GeS 2 based multi-component chalcogenide glasses, Ge–S–Sb(Cd), were prepared in series. With femtosecond time-resolved optical Kerr gate technique, we investigate their ultrafast third-order nonlinear optical (NLO) properties. The strongest NLO response comes from 0.70GeS 2–0.30Sb 2S 3. Its χ (3), 1.8 × 10 −12 esu, is more than three times to GeS 2 glass. Their instant NLO responses are within 120 fs pulse duration. We suggest that lone-pair electrons from highly polarizable Sb atom in [SbS 3] structure unit play an important role for the enhanced NLO response. This enhancement is much stronger to the contribution from S–S covalent bond.

Coherent oscillations in ultrafast fluorescence of photoactive yellow protein

The ultrafast photoinduced dynamics of photoactive yellow protein in aqueous solution were studied at room temperature by femtosecond fluorescence spectroscopy using an optical Kerr-gate technique. Coherent oscillations of the wave packet were directly observed in the two-dimensional time-energy map of ultrafast fluorescence with 180 fs time resolution and 5 nm spectral resolution. The two-dimensional map revealed that four or more oscillatory components exist within the broad bandwidth of the fluorescence spectrum, each of which is restricted in the respective narrow spectral region. Typical frequencies of the oscillatory modes are 50 and 120 cm(-1). In the landscape on the map, the oscillatory components were recognized as the ridges which were winding and descending with time. The amplitude of the oscillatory and winding behaviors is a few hundred cm(-1), which is the same order as the frequencies of the oscillations. The mean spectral positions of the oscillatory components in the two-dimensional map are well explained by considering the vibrational energies of intramolecular modes in the electronic ground state of the chromophore. The entire view of the wave packet oscillations and broadening in the electronic excited state, accompanied by fluorescence transitions to the vibrational sublevels belonging to the electronic ground state, was obtained.

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.

Ultrafast Dynamics of Exciton–Exciton and Exciton–Longitudinal Optical-Phonon Scattering Processes in ZnO Epitaxial Thin Films

Time-resolved luminescence spectra due to the exciton–exciton collision process were measured in ZnO thin films under excitonic resonant and band-to-band excitations by the optical Kerr gate technique. The luminescence due to the exciton–exciton collision process instantaneously emerges under excitonic resonant excitation, while it emerges with a delay of a few picoseconds under band-to-band excitation. The time delay observed indicates that, first, exciton–longitudinal optical (LO)-phonon scattering occurs and, then, the exciton–exciton collision process takes place after the completion of the thermal cooling of excitons through the cascade emission of multiple LO-phonons. The time delay is quantitatively evaluated by a simple calculation based on the exciton–LO-phonon scattering process.

Picosecond time-resolved imaging by nonscanning fluorescence Kerr gate microscope

A nonscanning picosecond fluorescence Kerr gate microscope has been developed. By applying the optical Kerr gate technique to the fluorescence imaging of microscopic samples, picosecond time-resolved fluorescence images were obtained with 1.4-ps time resolutions and 1-μm space resolutions, without XY scanning of the sample or the excitation light. A demonstrational measurement on an organic microcrystal, perylene, is presented.