Nonlinear Optical Performance Research Articles

Efficient tailored nonlinear optical responses by nanoassemblies: Focus on spindle β-FeOOH nanorods

Assemblies of β-iron oxyhydroxide (β-FeOOH) nanostructures were synthesized by a facile, mild, and non-toxic ultrasonication method. Quasi-rectangular, chrysanthemum-like, and silk-like architectures, respectively, were obtained by introducing a urea surfactant, synthesized Fe3O4 template, and natural kapok seed template. This versatile and efficient synthetic method can be extended to the fabrication of a series of novel, multifunctional assembled architectures. Hierarchical structures with identical morphologies were constructed from porous β-FeOOH nanorods with high surface areas. The effects of the assembly mode on the nonlinear optical (NLO) properties of the β-FeOOH nanorod assemblies were explored using the open-aperture Z-scan technique. Individual β-FeOOH nanorods and their analogous nanoassemblies exhibited excellent NLO performances upon excitation at 532 and 1064 nm in the nanosecond laser pulse regime, both in liquid and sol–gel solid-state matrices. These nanomaterials are promising candidates for broadband optical limiters; however, their abilities to attenuate intense and potentially dangerous laser beams differ. Our results confirm that nanoassembly formation can be used to effectively tailor the NLO activities of β-FeOOH nanorods, and the possible mechanisms for these behaviors are discussed. The observed NLO effects originate from nonlinear scattering and free-carrier absorption at 532 and 1064 nm, respectively. This study provides new insights into the assembly of one-dimensional building blocks, which will be useful in the rational design and preparation of hierarchical materials and enable tailoring and improvement of the NLO properties of materials.

Nonlinear optical responses of carbon quantum dots anchored on graphene oxide hybrid in solid-state transparent monolithic silica gel glasses

Exploring the nonlinear optical (NLO) response of graphene-based hybrids in solid-state three-dimensional macrostructures is vital to promote the practical development of graphene-based photonic and optoelectronic devices. Here, a solid-state hybrid of ultrafine and well-dispersed carbon quantum dots (CQDs) supported on graphene oxide (GO) was chosen as representative of such materials. The hybrid was introduced into organically modified silica gel glasses using a facile sol-gel wet chemical technique to obtain stable transparent monolithic nanocomposites, and their practical application in nonlinear optics was explored. The NLO performances were investigated by the open-aperture (OA) and closed-aperture (CA) Z-scan techniques in the nanosecond regime using a laser with a wavelength of 532 nm. The as-prepared CQD/GO SiO2 gel glasses displayed completely different NLO behavior from that of a CQD/GO suspension. The NLO performance of CQD/GO significantly improved after incorporation into SiO2 gel glasses because of the more graphitized structure of the CQD/GO hybrid. Both the OA and CA Z-scan patterns suggested that the NLO properties of the CQD/GO suspension combined nonlinear absorption and nonlinear scattering, while the NLO response of the CQD/GO SiO2 gel glasses stemmed primarily from nonlinear absorption and nonlinear refraction. In addition, this is the first report of the third-order nonlinear susceptibility χ(3) of a CQD/GO hybrid doped in solid-state gel glasses. The present results therefore demonstrate the feasibility and versatility of CQD/GO silica gel glasses, a promising new class of highly efficient NLO materials that can be applied in optical communications, radiofrequency optoelectronics, and all-optical signal processing.

Nonlinear optical performance of few-layer molybdenum diselenide as a slow-saturable absorber

Two-dimensional transition metal dichalcogenides are considered promising materials for next-generation photonics and nano-optical devices. Although many previous reports have shown saturable absorption of molybdenum diselenide (MoSe2), these nonlinear optical (NLO) properties of MoSe2 were measured in separate works and under different conditions with their hot-carrier relaxations. Here, we conducted a series of coherent studies on the NLO properties of few-layer MoSe2 via open-aperture Z-scan and degenerate pump-probe techniques. These measurements were taken to test the materials’ capabilities as a slow-saturable absorber. A slow-absorber model was employed to analyze the NLO measurements, and the results show that the NLO modulation depth was modeled to be 7.4% and 15.1% for the linear absorption coefficients of 5.22 cm−1 and 6.51 cm−1, respectively. The corresponding saturated intensities were modeled to be 39.37 MW/cm2 and 234.75 MW/cm2, respectively. The excitation carrier recovery time of few-layer MoSe2 was measured by degenerate pump-probe techniques to be ∼220 ps. These nonlinear optical performances make it a promising slow-saturable absorber for passive mode locking in femtosecond lasers.

Three hybrid tungstosilicates: Confinement of SiW12O404− anions in rigid concave surfaces with excellent nonlinear optical performance and interesting magnetic properties

Three novel polyoxoanion-based organic–inorganic compounds confined by the conjugate organic ligand tris(2-benzimidazylmethyl)amine (NTB) [Co(NTB)]2(SiW12O40)·4H2O (1) [Zn(NTB)]2(SiW12O40)·4H2O (2) and [Ni(NTB)(H2O)]2(SiW12O40)(C2H5OH)2·12H2O (3) have been synthesized successfully by using of hydrothermal synthesis. The penta-coordinate environment of metal ions for compound 1 and compound 2 leads to the formation of trigonal bipyramid, which was less to see in other polyoxoanion-based compounds. All three compounds are constituted of the [SiW12O40]4− unit and M(NTB) unit. The two-photon absorption (TPA) cross section σ value of three compounds are calculated as 1826, 2253 and 1470 GM (1 GM = 10−50 cm4 s/photon), respectively. The compound 2 reveals the biggest σ value among the NTB-modified POMs. Furthermore, the compounds 1 and 3 show intriguing paramagnetic performance. The effect of different metal ions on optical property would also be investigated.

Coordination-induced broadband optical nonlinearity through axial bonding of pyridine anchored methine-bridged polypyrrole to metal-porphyrins

A facile route to assemble pyridine anchored methine-bridged polypyrrole to metal-porphyrins through axial bonding has been demonstrated, and the as-prepared nanocomposites exhibit very distinctive broadband nonlinear optical performances compared to their precursors at both 532 and 1064 nm, due to an accumulation effect.

CaB5O7F3: A Beryllium-Free Alkaline-Earth Fluorooxoborate Exhibiting Excellent Nonlinear Optical Performances.

Noncentrosymmetric (NCS) fluorooxoborates are one of the most attractive systems for discovering the new deep-ultraviolet (DUV) nonlinear optical (NLO) materials. Here, we report the formation, crystal structure, and optical properties of a new NCS alkaline earth fluorooxoborate: CaB5O7F3. It exhibits excellent NLO performances including large band gap (8.75 eV), large second harmonic generation intensity (2 × KH2PO4 and 0.4 × β-BaB2O4, under 1064 and 532 nm radiation, respectively), and moderate birefringence (0.07 @ 1064 nm) that enables frequency doubling down to 183 nm. It demonstrates that CaB5O7F3 is a promising DUV NLO material.

Z-Scan Study on a Silver Nanoparticles Embedded TeO<sub>2</sub>-SiO<sub>2</sub> Glass Prepared by Sol-Gel Method

An inserted type Ag/TeO2-SiO2composite gel glass was prepared through silver nanoparticles embedded in TeO2-SiO2composite gel. The silver nanoparticles were prepared previously by ascorbic acid deoxygenates AgNO3solution and mixed into TeO2-SiO2composite sol which was prepared in aqueous system using TeO2and tetraethoxysilane as precursors, and then the inserted type Ag/TeO2-SiO2composite gel glass was produced through sol aging and molding. The silver nanoparticles which dispersed in the TeO2-SiO2gel substrate made the composite glass having excellent nonlinear optical properties. The nonlinear optical parameters was tested by Z-scan technique using 15 ps laser pulses at the wavelength of 532 nm. The surface morphology was characterized by SEM. The results identified that spherical Ag nanoparticles with the size about 50-100 nm dispersed in the TeO2-SiO2gel. In the Ag/TeO2-SiO2material, the doped structure and the trigonal bipyramid structure of TeO2was the important factor for the excellent nonlinear optical performance.

Controllable Photoluminescent and Nonlinear Optical Properties of Polymerizable Carbon Dots and Their Arbitrary Copolymerized Gel Glasses

AbstractIn this work, an efficient method is developed to prepare silane‐functionalized red‐emissive carbon dots and carbon dots gel glasses with arbitrary loading fraction (0–100%). The as‐prepared materials possess strong photoluminescence and significant third‐order nonlinear optical performances. The optical properties can be tuned by either changing solvents and pH of the solution or adjusting the loading fractions of carbon dots in gel glasses. In particular, the photoluminescence of the carbon dots and their polymerized glasses can be linearly modulated from yellow to red emission by increasing the loading fraction of carbon dots or the polarity of solvent. It is also found that the chemical copolymerization leads to superior optical properties of gel glasses to that of the carbon dots solution, because the copolymerization endows stable immobilization of carbon dots in a rigid matrix. This study provides a feasible method to prepare optoelectronic hybrid materials and devices.

Q-switched Yb3+:YAG laser using plasmonic Cu2-xSe quantum dots as saturable absorbers

Cu2-xSe quantum dots (QDs) were synthesized by organometallic synthesis methods. Due to heavy self-doping, the Cu2-xSe QDs exhibit particle plasmon resonance in the near-infrared. Transient absorption spectroscopic investigation revealed strong nonlinear optical absorption and bleaching performance of the QDs under femtosecond pulse excitation, which enabled the Cu2-xSe QDs to be excellent saturable absorbers and applied in Q-switched or mode-locked lasers. A passively Q-switched Yb3+:YAG solid-state laser at 1.03 μm was achieved by coating Cu2-xSe QDs as saturable absorbers onto one of the output coupler of the V-shaped linear cavity.

Evaluating the component contribution to nonlinear optical performances using stable [Ni4O4] cuboidal clusters as models.

Five stable clusters sharing the cuboidal [Ni4O4] skeleton are subjected to third-order nonlinear optical (NLO) property measurements. Preliminary results suggest that the NLO property is largely defined by the cluster core skeleton and the directly coordinated atoms, with limited contribution from the heavy atoms peripherally attached to the aromatic ligands.

Photo-induced resonance energy transfer and nonlinear optical response in ball-type phthalocyanine conjugated to semiconductor and graphene quantum dots

Ball-type zinc and gallium phthalocyanines were covalently linked to graphene and semiconductor quantum dots resulting in enhanced triplet parameters and nonlinear optical performance.

Janus molecules: large second-order nonlinear optical performance, good temporal stability, excellent thermal stability and spherical structure with optimized dendrimer structure

A Janus molecule J2 containing five FTC moieties exhibited good thermal stability, excellent electro-optic performance and good temporal stability.

Na3Ca4(TeO3)(PO4)3: a new noncentrosymmetric tellurite phosphate with fascinating multimember-ring architectures and intriguing nonlinear optical performance.

A new functional compound Na3Ca4(TeO3)(PO4)3 has been successfully synthesized and fully characterized. It is the first example of a tellurite phosphate that exhibits a fascinating multimember-ring configuration. Moreover, a careful theoretical and experimental study also reveals the intriguing nonlinear optical performance of Na3Ca4(TeO3)(PO4)3.

A rigid ringlike molecule: large second-order nonlinear optical performance, good temporal and thermal stability, and ideal spherical structure conforming to the “site isolation” principle

Ringlike molecule R1 containing two FTC moieties exhibited excellent EO performance (d33 = 562 pm V−1 @1950 nm, T80% = 145 °C).

Four new quaternary chalcogenides A2Ba7Sn4Q16 (A = Li, Na; Q = S, Se): syntheses, crystal structures determination, nonlinear optical performances investigation

Four new quaternary chalcogenides with interesting structures and potential nonlinear optical performances were synthesized for the first time.

Facet-dependent nonlinear optical properties of bismuth oxychloride single-crystal nanosheets

Single-crystal nanosheets of BiOCl with preferentially exposed {001} and {010} facets were synthesized, and their third-order nonlinear optical performances were evaluated by Z-scan measurements.

Tailoring the nonlinear optical performance of two-dimensional MoS2 nanofilms via defect engineering

Defect engineering plays a key role in determining the catalytic and optical properties of two-dimensional (2D) materials such as molybdenum disulfide (MoS2) in their practical applications in optical and photonic devices. Here, we report a direct strategy for the fabrication of wafer-scale 2D MoS2 nanofilms with tunable sulfur (S) vacancies and crystallinity by a modified solvothermal method via a polyelectrolyte-assisted annealing process. Our results demonstrate that the S vacancies in MoS2 nanofilms can induce saturable absorption (SA) in MoS2 by introducing new energy bands within the band gap of MoS2, and the crystallinity has a significant effect on the two-photon absorption (TPA) coefficient of MoS2 nanofilms. The SA responses in MoS2 will gradually dominate the nonlinear optical (NLO) behavior of MoS2 with a lower saturable intensity along with increasing the S vacancies. The TPA coefficient of the MoS2 nanofilms with increased crystallinity is improved to (4.3 ± 0.5) × 102 cm GW-1 on increasing the crystallinity of MoS2 films, over four times larger than that of their counterpart with relatively low crystallinity. Additionally, the damage threshold of MoS2 nanofilms after polyelectrolyte-assisted annealing treatment is greatly improved to ∼74.1 GW cm-2 compared to ∼32.6 GW cm-2 of their counterpart with few S vacancies and relatively low crystallinity, due to the increased crystallinity and partial oxidation of MoS2. This work sheds light on how the defects tailor the nonlinear optical properties of 2D MoS2 nanofilms and affords an effective strategy for defect engineering via a polyelectrolyte-assisted annealing process, which can be applied to other 2D transition metal dichalcogenides.

Synergistically Enhanced Optical Limiting Property of Graphene Oxide Hybrid Materials Functionalized with Pt Complexes.

Recently, graphene-based materials have become well-known nonlinear optical materials for the potential application of laser protection. Two new graphene oxide-platinum complex (GO-Pt) hybrid materials (GO-Pt-1, GO-Pt-2) have been fabricated through covalent modification and electrostatic adsorption of different Pt complexes with GO. The structural and photophysical properties of the resultant hybrid materials were studied. The nonlinear optical properties and optical power limiting (OPL) performance of Pt complexes, GO, and GO-Pt hybrid materials were investigated by using Z-scan measurements at 532 nm. At the same transmittance, the results illustrate that functionalization of GO makes GO-Pt hybrid materials possess better nonlinear optical properties and OPL performance than individual Pt complexes and GO due to a combination of nonlinear scattering, nonlinear absorption, and photoinduced electron and energy transfer between GO and Pt complex moieties. Furthermore, the nonlinear optics and OPL performance of GO-Pt-2 are better than those of GO-Pt-1, due to not only the excellent optical limiting of Pt-2 and more molecules per area of GO but also the way of combination of Pt-2 and GO.

Covalent-linked porphyrin/single-walled carbon nanotube nanohybrids: synthesis and influence of porphyrin substituents on nonlinear optical performance

Electron-withdrawing 4-cyanophenyl-, electronically innocent phenyl-, and electron-donating 4-dimethylaminophenyl-functionalized porphyrin/single-walled carbon nanotube (SWCNT) nanohybrids have been synthesized and characterized by ultraviolet–visible absorption, steady-state fluorescence, Fourier transform infrared, and Raman spectroscopies, X-ray photoelectron spectroscopy, scanning electron microscopy, transmission electron microscopy and thermogravimetric analysis. Nonlinear optical (NLO) studies using the Z-scan technique revealed that both the cyano (CN) and the dimethylamino (DMA) substituents have a positive effect in optimizing the optical limiting performance of the SWCNT–porphyrin nanohybrids, owing to increased reverse saturable absorption (RSA) of the porphyrin moieties after functionalization by CN or DMA. In comparison with CN, the DMA group has a more positive influence on the porphyrin excited states and thereby the RSA and NLO activity.

Accessible fabrication and mechanism insight of heterostructured BiOCl/Bi2MoO6/g-C3N4 nanocomposites with efficient photosensitized activity

Semiconductor nanostructures perform wide applications in light-driven physical and chemical processes; the photophysical and chemical properties of semiconductors can be adjusted by changing their shape, size and composition. To investigate the effect of g-C3N4 loadings on the nonlinear optical and photocatalytic performances, a series of novel BiOCl/Bi2MoO6/g-C3N4 nanocomposites loaded with different g-C3N4 contents was prepared via a facile refluxing process. The existence of strong interfacial interactions between BiOCl/Bi2MoO6 and g-C3N4 was confirmed by a series of characterization techniques including X-ray photoelectron spectroscopy and UV-vis diffuse reflectance spectroscopy. The electrochemical impedance spectroscopy, photoluminescence and nanosecond time-resolved emission confirmed that the interface charge separation efficiency of BiOCl/Bi2MoO6/0.10C3N4 was greatly improved, resulting in a higher activity toward photodegradation of Rhodamine B and a higher photocurrent density. The associated photocatalytic activity of BiOCl/Bi2MoO6/g-C3N4 nanocomposites is shown to be dependent on the g-C3N4 loadings. An improved nonlinear optical performance was also observed for BiOCl/Bi2MoO6/0.10C3N4 nanocomposite. These results reveal the photosensitized mechanisms of BiOCl/Bi2MoO6/g-C3N4, and demonstrate their practical use as recyclable photocatalyst and optical limiters. This method may usher a new phase for the preparation of novel and highly efficient ternary heterostructures for energy conversion, light harvesting and optical limiting applications.