Ultrafast Third-order Nonlinear Optical Response Research Articles

Enhancing the Ultrafast Third-Order Nonlinear Optical Response by Charge Transfer in VSe2-Reduced Graphene Oxide Hybrid

Enhancing the Ultrafast Third-Order Nonlinear Optical Response by Charge Transfer in VSe₂-Reduced Graphene Oxide Hybrid

Ultrafast third-order nonlinear optical response of charge coupled gold nanoparticle-Ge24Se76 heterostructure

Ultrafast third-order nonlinear optical response of charge coupled gold nanoparticle-Ge24Se76 heterostructure

Single-Wall-Carbon-Nanotube– VSe2 Nanohybrid for Ultrafast Visible-To-Near-Infrared Third-Order Nonlinear Optical Limiters

An ideal third-order nonlinear optical material, which can efficiently absorb and refract light over a broad spectral range, is of both fundamental and technological significance as it enables many helpful functionalities in photonics. However, the optical nonlinearities are rather weak due to their perturbative nature and are limited to electronic resonances, thus restricting the response to a narrow spectral range. A charge-coupled donor-acceptor material pair can enhance the nonlinear optical response and circumvent the narrow spectral range limitation. However, such studies on potential material pairs remain largely unexplored. Here, we report the experimental observation of ultrafast third-order nonlinear optical response spanning the entire visible-to-near-infrared (400--900 nm) region in single-wall-carbon-nanotube (SWCNT)--${\mathrm{VSe}}_{2}$ nanohybrid in the strong coupling regime, enabled by efficient charge transfer. Compared to control systems, the measured nonlinear absorption and refraction of the nanohybrid show unprecedented or many-fold enhancements. Further, our density-functional theory and Bader-charge analysis show the strong electronic coupling of the nanohybrid in which the electrons are transferred from ${\mathrm{VSe}}_{2}$ to SWCNT, verified by steady-state and time-resolved photoluminescence measurements. The physics of the ultrafast nonlinear optical response is well captured by our five-level rate-equation model both qualitatively and quantitatively. Using the nanohybrid, we design a liquid cell-based optical limiter with an order of magnitude better device performance parameters, such as the optical limiting onset ($2.5--8.0\phantom{\rule{0.2em}{0ex}}\mathrm{mJ}\phantom{\rule{0.2em}{0ex}}{\mathrm{cm}}^{\ensuremath{-}2}$) and the differential transmittance ($0.42--0.62$), compared to several other benchmark optical limiters in the femtosecond regime.

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.

Ultrafast third-order nonlinear optical response of Ag modified ZnSe/ZnS core-shell structure quantum dots composite films

ZnSe/ZnS/Ag composite films were prepared on quartz substrates by magnetron sputtering and spin coating techniques.The morphology of Ag nanoparticles (NPs) with different sputtering powers and the dispersion of ZnSe/ZnS quantum dots (QDs) at different concentrations were observed by SEM and TEM. The linear absorption spectra shows the composite films which modified by Ag NPs had a blue shifted compared with the single ZnSe/ZnS QDs.The Z-scan results showed that the saturated absorption(SA) characteristics of the composite films modified by Ag NPs were significantly enhanced.The SA intensity of the composite films can be adjusted by appropriate increase the concentration of QDs, increasing the sputtering power of Ag NPs and incident laser power.By calculating the nonlinear absorption coefficients of the composite films under different conditions, it is found that increasing the excitation power is the most effective way to improve the SA property of the composite films. Compared with the single ZnSe/ZnS QDs, the βeff value of the composite films is increased by 104 orders of magnitude, which makes the ZnSe/ZnS QDs more widely used in the field of nonlinear optical devices.

Ultrafast Third-Order Nonlinear Optical Response Excited by fs Laser Pulses at 1550 nm in GaN Crystals.

The ultrafast third-order optical nonlinearity of c-plane GaN crystal, excited by ultrashort (fs) high-repetition-rate laser pulses at 1550 nm, wavelength important for optical communications, is investigated for the first time by optical third-harmonic generation in non-phase-matching conditions. As the thermo-optic effect that can arise in the sample by cumulative thermal effects induced by high-repetition-rate laser pulses cannot be responsible for the third-harmonic generation, the ultrafast nonlinear optical effect of solely electronic origin is the only one involved in this process. The third-order nonlinear optical susceptibility of GaN crystal responsible for the third-harmonic generation process, an important indicative parameter for the potential use of this material in ultrafast photonic functionalities, is determined.

Ultrafast Nonlinear Optical and Structure-Property Relationship Studies of Pyridine-Based Anthracene Chalcones Using Z-Scan, Degenerate Four-Wave Mixing, and Computational Approaches.

The structural, thermal, linear, and femtosecond third-order nonlinear optical (NLO) properties of two pyridine-based anthracene chalcones, (2E)-1-(anthracen-9-yl)-3-(pyridin-2-yl)prop-2-en-1-one (2PANC) and (2E)-1-(anthracen-9-yl)-3-(pyridin-3-yl)prop-2-en-1-one (3PANC), were investigated. These two chalcones were synthesized following the Claisen-Schmidt condensation method. Optically transparent single crystals were achieved using a slow evaporation solution growth technique. The presence of functional groups in these molecules was established by Fourier transform infrared and NMR spectroscopic data. The detailed solid-state structure of both chalcones was determined from the single-crystal X-ray diffraction data. Both crystals crystallized in the centrosymmetric triclinic space group P1̅ with the nuance of unit cell parameters. The crystals (labeled as 2PANC and 3PANC) have been found to be transparent optically [in the entire visible spectral region] and were found to be thermally stable up to 169 and 194 °C, respectively. The intermolecular interactions were investigated using the Hirshfeld surface analysis, and the band structures (highest occupied molecular orbital-lowest unoccupied molecular orbital, excited-state energies, global chemical reactivity descriptors, and molecular electrostatic potentials) were studied using density functional theory (DFT) techniques. The ultrafast third-order NLO properties were investigated using (a) Z-scan and (b) degenerate four-wave mixing (DFWM) techniques using ∼50 fs pulses at 800 nm (1 kHz, ∼4 mJ) from a Ti:sapphire laser amplifier. Two-photon-assisted reverse saturable absorption, self-focusing nonlinear refraction, optical limiting, and optical switching behaviors were witnessed from the Z-scan data. 3PANC demonstrated a stronger two-photon absorption coefficient, while 2PANC depicted a stronger nonlinear refractive index among the two. The time-resolved DFWM data demonstrated that the decay times of 2PANC and 3PANC were ∼162 and ∼180 fs, respectively. The second hyperpolarizability (γ) values determined by DFT, Z-scan, and DFWM were found to be in good correlation (with a magnitude of ∼10-34 esu). The ultrafast third-order NLO response, significant NLO properties, and thermal stability of these chalcones brands them as potential candidates for optical power limiting and switching applications.

Ultrafast direct charge transfers mediated modification of third order nonlinear optical response in Sb2Se3–Au core shell nanorods

Realization of the direct charge transfer at metal–semiconductor interfaces is a long-standing goal of both fundamental and technological significance. Here we report the synthesis of a colloidal Sb2Se3–Au core–shell nanorod as a model system to demonstrate an efficient direct charge transfer from an Au shell to Sb2Se3 core when the metal is selectively excited at the plasmonic wavelength. In our experiments, direct charge transfer by the Landau damping of the plasmons of metal shell significantly enhances the excited state population that results in an unprecedented ultrafast third-order nonlinear optical response as a function of the plasmon-excitation detuning wavelength. The single step photo-induced charge transfer analogous to the intramolecular electronic transition in molecules is probed by ultrafast transient absorption, which reveals that the electrons are directly transferred from the Fermi level of Au to the unoccupied levels of Sb2Se3 in less than 150 fs. First principles density functional theory calculations indicate that the hybridized eigenstates of the strongly coupled system are delocalized across the metal–semiconductor interfaces. By formulating the theoretical models, we connect our experimental results to the theory.

Ultrafast third-order nonlinear optical response of CdSe/Al2O3/Ag composite films

The CdSe/Al2O3/Ag composite films were deposited by magnetron sputtering and spin coating, and some samples were annealed at 450 °C. The linear absorption peak of annealed samples showed a clear redshift behavior. The femtosecond Z-scan was adopted to study the ultrafast third-order nonlinear optical response of the CdSe/Al2O3/Ag composite films. In the present study, the nonlinear properties of the composite films were 104 times higher than single CdSe quantum dots, and the properties exhibited by the unannealed samples were better than annealed samples. The increase in laser energy causes an enhancement in saturation absorption and self-focusing properties. The effects of Ag nanoparticles sputtering conditions and CdSe quantum dots content on the optical properties of the samples were also investigated. Unannealed CdSe/Al2O3/Ag composite films with Ag nanoparticles (P = 15 W) and one layer of CdSe quantum dots have the maximum value of β and χ3,which are -4.80 × 10−9m/W and 3.82 × 10−9esu. Composite films can be used in optical sensing, information and communication technologies, and many other optoelectronic applications.

Synthesis, Theoretical Investigation and Ultrafast Third-Order Nonlinear Optical Response of 2-(Pyren-1-yl)-1,8-naphthyridine

Synthesis, Theoretical Investigation and Ultrafast Third-Order Nonlinear Optical Response of 2-(Pyren-1-yl)-1,8-naphthyridine

Revealing of the ultrafast third-order nonlinear optical response and enabled photonic application in two-dimensional tin sulfide

Black phosphorus (BP), a typical mono-elemental and two-dimensional (2D) material, has gathered significant attention owing to its distinct optoelectronic properties and promising applications, despite its main obstacle of long-term stability. Consequently, BP-analog materials with long-term chemical stability show additional potential. In this contribution, tin sulfide (SnS), a novel two-elemental and 2D structural BP-analog monochalcogenide, has been demonstrated to show enhanced stability under ambient conditions. The broadband nonlinear optical properties and carrier dynamics have been systematically investigated via Z-scan and transient absorption approaches. The excellent nonlinear absorption coefficient of 50.5×10−3 cm/GW, 1 order of magnitude larger than that of BP, endows the promising application of SnS in ultrafast laser generation. Two different decay times of τ1∼873 fs and τ2∼96.9 ps allow the alteration between pure Q switching and continuous-wave (CW) mode locking in an identical laser resonator. Both mode-locked and Q-switched operations have been experimentally demonstrated using an SnS saturable absorber at the telecommunication window. Femtosecond laser pulses with tunable wavelength and high stability are easily obtained, suggesting the promising potential of SnS as an efficient optical modulator for ultrafast photonics. This primary investigation may be considered an important step towards stable and high-performance BP-analog material-based photonic devices.

Synthesis of Two Ferrocene-Based Chalcone Derivatives and Their Ultrafast Third-Order Nonlinear Optical Response

Synthesis of Two Ferrocene-Based Chalcone Derivatives and Their Ultrafast Third-Order Nonlinear Optical Response

Intensity mediated change in the sign of ultrafast third-order nonlinear optical response in As2S2 thin films.

We study experimentally and theoretically the intensity-dependent off-resonant ultrafast third-order nonlinear optical response of As2S2 thin films. At low intensity, we observed saturable absorption with a negative (self-defocusing) nonlinear refractive index (n2) which at higher intensity switched over to reverse saturable absorption with a change in the sign of n2 to positive (self-focusing). Our findings constitute compelling evidence on how to dynamically tune the optical response with the intensity that has its origin in the combined effect of two-photon absorption and Pauli blocking. The results were explained with the help of time-resolved measurements and rigorous theoretical and numerical simulations.

Impact of electronegative character on ultrafast nonlinear optical absorption of azine derivatives

Two azine derivatives (NO(Cl) and NS(Cl)) with different electronegative central core were prepared and spectroscopically characterized. Their ultrafast third-order nonlinear optical (NLO) responses were investigated using open aperture Z-scan and optical limiting method with 190 fs laser pulses at 515 nm. The frontier molecular orbitals and energy gaps of samples were obtained through quantum chemical calculation. Transient absorption spectra demonstrated that the origin of strong NLO absorption of two molecules was attributed to excited-state absorption. A simplified three-energy-level model was used to determine their photo-physical parameters. Our results show that the stronger the electronegative cationic groups is, the stronger the NLO absorption performs. The azine compounds have large excited-state lifetime and large ratio of singlet excited-state absorption cross-section to that of ground state cross-section (∼20.2), indicating it is a candidate material for future ultrafast optical limiters.

Thickness dependence of a giant nonlinear saturable absorption response in GeSb4Te7 thin films

Nonlinear optical absorption (NOA) materials with large saturable absorption response and high damage threshold are useful for a variety of applications such as ultrafast nonlinear optical devices and laser mode lockers. In this study, a suite of GeSb4Te7 thin films with different thicknesses were prepared, and the surface morphology, structure and linear optical absorption of these films were investigated in detail. Through an open aperture Z-scan technique with femtosecond pulses at 800 nm wavelength, it is found that effective NOA coefficient as high as −93 009 cm GW−1 can be achieved in GeSb4Te7 thin films. Besides, GeSb4Te7 thin films exhibit a giant and ultrafast third-order nonlinear optical saturable absorption response due to significant band filling effect. Especially, NOA response, coefficient and damage threshold can be well controlled by adjusting the film thickness. Both stability and efficiency can be acquired by thermal treatment.

Ultrafast third-order nonlinear optical response of pyrene derivatives

Two mono-substituted pyrene derivatives with delocalized electron system 1-(pyren-1-yl)−3-(4-Methyl thiophene-2-yl) acrylic ketone (13#) and 1-(pyren-1-yl)−3-(4-bromo thiophene-2-yl) acrylic ketone (15#) were successfully synthesized. The resultant compounds were characterized by nuclear magnetic resonance (NMR), infrared spectroscopy (IR), high resolution mass spectrum (HR-MS), and UV–vis spectra. The third-order nonlinear optical properties of the compounds were investigated using Z-scan technique with femtosecond laser pulses at 500nm and 700nm, respectively. Both of the compounds showed a decrease in transmittance about the focus, which are typical of two-photon absorption. It was found that the two-photon absorption behavior of the pyrene derivatives were modified by substituents on thiophene ring. These results indicate that both compounds can be promising candidates for future optoelectronic and bio-imaging applications.

Nonlinear Optical Properties and Ultrafast Dynamics of Undoped and Doped Bulk SiC

Ultrafast third-order nonlinear optical response of bulk 6H-SiC undoped and doped with different nitrogen concentrations are investigated utilizing femtosecond Z-scan and optical Kerr effect (OKE) techniques at the wavelength of 800nm. The Z-scan measurement shows that the third-order nonlinear optical susceptibilities of the doped samples are improved in comparison to the intrinsic sample. The OKE results additionally reveal that the instantaneous nonlinear optical response of the samples can be ascribed to the distortion of the electron cloud. The ultrafast transient spectroscopic measurements with the one-color and two-color pump-probe techniques demonstrate that the ultrafast recovery process in subpicosecond domain is induced by two-photon absorption process, while the slow relaxation component reflects the carrier dynamics of the excited electrons.

Ultrafast non-resonant third-order optical nonlinearity of [formula omitted]– [formula omitted]–CdS chalcogenide glass

Ultrafast third-order nonlinear optical responses of 4(1− x)/5GeS 2-(1− x)/5Ga 2S 3- xCdS ( x=0.05, 0.10 and 0.15 in mol%) chalcogenide glasses was investigated by using the femtosecond time-resolved optical Kerr effect technique at a wavelength of 800 nm. The largest third-order nonlinear susceptibility of all samples was estimated to be 1.65×10 −13 esu. An ultrafast nonlinear response time of about 250 fs was observed, which was dominantly assigned to the ultrafast distortion of the electron cloud under femtosecond laser excitation. A nonlinear relationship between the third-order nonlinear susceptibility and the introduced amount of CdS was discussed, suggesting a possible disturbance between different polarizable bonds in the glass system.

Large optical Kerr effect in bulk GeSe 2–In 2Se 3–CsI chalcohalide glasses

Third-order nonlinear optical properties of GeSe 2–In 2Se 3–CsI chalcogenide bulk glasses are studied by Standard pico-second (ps) time-resolved optical Kerr effect (OKE) technique. The obtained χ (3) and n 2 at 1064 nm of the glass 72.25GeSe 2–23.75In 2Se 3–5CsI are as large as 10.07 × 10 −12 esu and 6.5 × 10 −18 m 2/W, respectively, more than twice that of As 2S 3 glass. The relationship between glass compositions and the third-order nonlinear optical responses was analyzed by Raman spectra in terms of structural evolution. It is suggested that the tetrahedral units ([GeSe 4] and [InSe 4]) play an important role in the ultrafast third-order nonlinear optical responses of these chalcohalide glasses.

Third-order nonlinearities in GeSe 2–In 2Se 3–CsI glasses for telecommunications applications

Ultrafast third-order nonlinear optical responses of GeSe 2–In 2Se 3–CsI chalcohalide glasses have been measured by using optical Kerr effect (OKE) technique at 1064 nm. The obtained third-order nonlinear susceptibility χ (3) and nonlinear refractive index n 2 are as large as 9.46 × 10 −12 esu and 6.5 × 10 −14 cm 2/W, respectively. The relationship between glass compositions and the third-order nonlinear optical responses was analyzed by Raman spectra in terms of structural evolution. It is suggested that the tetrahedral units play an important role in the ultrafast third-order nonlinear optical responses of these chalcohalide glasses. The present glass is a promising material for all-optical switching devices.