Optical Limiting Response Research Articles

Optical Limiting Response of Porous Carbon Dispersions.

With the wide application of intense lasers, the protection of human eyes and detectors from laser damage is becoming more and more strict. In this paper, we study the nonlinear optical limiting (OL) properties of porous carbon with a super large specific surface area (2.9 × 103 m2/g) using the nanosecond Z-scan technique. Compared to the traditional OL material C60, the porous carbon material shows an excellent broadband limiting effect, and the limiting thresholds correspond to 0.11 J/cm2 for 532 nm and 0.25 J/cm2 for 1064 nm pulses, respectively. The nonlinear scattering experiments showed that the OL behavior was mainly attributed to the nonlinear scattering effect, which is caused by the rapid growth and expansion of bubbles in the dispersion induced by laser irradiation, and the scattered light distribution is consistent with the results of Mie's scattering. These results suggest that porous carbon materials are expected to be applied to the field of laser protection in the future to further protect the human eye and precision optical instruments.

Pulse-width-dependent optical limiting properties of a novel twist-acene compound

Organic materials with large nonlinear optical coefficient and ultrafast response speed have attracted considerable attention due to their potential applications in optical limiting (OL). However, it is a challenging obstacle to develop a candidate material with optimal nonlinear absorption response while avoiding undesirable low transmittance. Here, a novel symmetrical heteroacenes compound 4,4'-(buta-1,3-diyne-1,4-diylbis(2,7-di-tert-butyl-9,14-diphenyldibenzo[de,qr]tetracene-12,11-diyl))bis(N,N-diphenylaniline)(abbreviated as JPC-42) was synthesized and its nonlinear optical properties were investigated under different pulse-width excitation conditions at 532 nm. Results show that the compound with twisted structure displays superior optical limiting response in which extremely high transmittance (91% in 532 nm) and low OL threshold (3 × 10−3 J/cm2 in femtosecond regime, 130 × 10−3 J/cm2 in picosecond regime) are obtained. Our results demonstrate that this twist-acene compound is a promising candidate in laser protection fields.

Z-Scan Measurements and Optical Limiting Response of V2O5:MoO3 Thin Films

Z-Scan Measurements and Optical Limiting Response of V2O5:MoO3 Thin Films

Interpenetrated Metal-Porphyrinic Framework for Enhanced Nonlinear Optical Limiting.

Structural interpenetration in metal-organic frameworks (MOFs) significantly impacts on their properties and functionalities. However, understanding the interpenetration on third-order nonlinear optics (NLO) of MOFs have not been reported to date. Herein, we report two 3D porphyrinic MOFs, a 2-fold interpenetrated [Zn2(TPyP)(AC)2] (ZnTPyP-1) and a noninterpenetrated [Zn3(TPyP)(H2O)2(C2O4)2] (ZnTPyP-2), constructed from 5,10,15,20-tetra(4-pyridyl)porphyrin (TPyP(H2)) and Zn(NO3)2 (AC = acetate, C2O4 = oxalate). ZnTPyP-1 achieves excellent optical limiting (OL) performance with a giant nonlinear absorption coefficient (3.61 × 106 cm/GW) and large third-order susceptibility (7.73 × 10-7 esu), which is much better than ZnTPyP-2 and other reported OL materials. The corresponding MOFs nanosheets are dispersed into a polydimethylsiloxane (PDMS) matrix to form highly transparent and flexible MOFs/PDMS glasses for practical OL application. In addition, the OL response optimized by adjusting the MOFs concentration in the PDMS matrix and the type of metalloporphyrin are discussed in the ZnTPyP-1 system. The theoretical calculation confirmed that the abundant π-π interaction from porphyrinic groups in the interpenetrated framework increased the electron delocalization/transfer and boosted the OL performance. This study opens a new avenue to enhance OL performance by the construction of interpenetrated structures and provides a new approach for the preparation of transparent and flexible MOF composites in nonlinear optical applications.

The effect of laser wavelength and concentration on the optical limiting response of exfoliated MoS2 in the NMP solvent

This study investigated the optical limiting (OL) response of the dispersion of MoS2 nanosheets in N-methyl-2-pyrrolidone (NMP) which was made by liquid-phase exfoliation. We measured the OL response of different concentrations of the samples at two wavelengths of 405 nm and 532 nm using a continuous wave (CW) laser irradiation. It was observed that the value of the OL threshold changes by changing the laser wavelength and MoS2 concentration. To understand the mechanisms underlying these results, we use the spatial self-phase modulation (SSPM) and the Z-scan methods to measure the nonlinear absorption and refraction coefficients. It was revealed that the nonlinear absorption response is too weak. These findings highlight the significant role of the nonlinear refraction effect in the spatial self-phase modulation and the OL response of MoS2 dispersion under low-power laser irradiation.

Composition-dependent optical limiting behavior of all-inorganic halide perovskite quantum dots

Abstract Nonlinear optical nanostructured materials are gaining interest as optical limiters for various applications. Here, all-inorganic halide perovskite quantum dots (PQDs, SiO2@CsPbX3 (X = Cl, Br, I) QDs) with tunable composition were prepared via ligand assisted reprecipitation, using 3-aminopropyltriethoxysilane as a ligand. The formation of the SiO2@CsPbX3 QDs was confirmed by transmission electron microscopy, X-ray diffraction, infrared spectroscopy, ultraviolet–visible absorption spectroscopy and photoluminescence spectroscopy. The composition-dependent optical limiting (OL) behavior of the SiO2@CsPbX3 QDs was observed using nanosecond and picosecond laser pulses at a wavelength of 532 nm. The SiO2@CsPbBr3 QDs exhibit favorable OL properties. Their OL threshold for the nanosecond laser pulse is 1.68 J/cm2, which is comparable to that of carbon nanotube suspension (a benchmark optical limiter). The presence of chloride or iodide in the SiO2@CsPbX3 QDs leads to weaker OL performance. The OL behavior of the SiO2@CsPbBr3 QDs is attributed to the narrow band gap, large average size, abundant charge carriers under laser excitation and high stability. The OL mechanism was investigated using the open-aperture and closed-aperture techniques. The OL behavior of the SiO2@CsPbX3 QDs is largely attributed to the combined mechanisms of nonlinear absorption and nonlinear refraction. These results reveal the physical processes of the composition-dependent OL properties of the CsPbX3 QDs. These findings provide a means to tailor the OL response of PQDs by controlling the halide ion ratio.

Novel nitro based chalcone derivative single crystals: characterization on structural, linear optical, thermal, and third-order nonlinear optical properties

Crystals of “(2E)-1-(4-nitrophenyl)-3-(2,3,4-trimethoxyphenyl)prop-2-en-1-one” (NPTMP) are grown by slow solvent evaporation technique. The compound purity and presence of functional group elements in the material were identified from the spectroscopic techniques (FT-IR and ˡH-NMR). The single-phase formation in the bulk powder crystalline sample has been confirmed from powder XRD analysis. The intermolecular interaction and structure-related parameters were obtained and analyzed by utilizing single-crystal XRD data. Using single-crystal XRD data (CIF file), display of the intermolecular interactions and contribution of H···H and H···O/O···H interaction have been obtained. The molecule is mapped over dnorm, de, di, curvedness, shape index, and electrostatic potential by generating the Hirshfeld’s surface of NPTMP molecule. The linear optical absorbance and optical bandgap of the material have been confirmed by UV–VIS–NIR spectroscopic technique. The thermal stability of the crystal NPTMP is obtained from TGA/DTA/DSC techniques. The surface morphology of the crystal is collected from scanning electron microscopy (SEM) and the electronic contribution of hyperpolarizability parameters is obtained from MOPAC 2016 software. The third-order nonlinear optical properties were studied by the Z-scan technique using CW DPSS laser operating at 532 nm wavelength. The molecule exhibits a comparatively moderate optical limiting response due to reverse saturable absorption (RSA).

Penta(zinc porphyrin)[60]fullerenes: Strong reverse saturable absorption for optical limiting applications

Penta(zinc porphyrin)[60]fullerene, in which a fullerene (C60) with attached five electron donating zinc porphyrin moieties was synthesized. The nonlinear optical response was studied together with reference penta(trimethylsilyl)C60 and triazole-zinc porphyrin compounds. The second and third harmonic generation in both guest-host polymeric films deposited by means of spin coating technique and films obtained by physical vapor deposition technique was investigated via Maker fringe technique employing 30 ps laser pulses at 1064 nm. The second and third order susceptibilities as well as second hyperpolarizabilities were determined. Penta(zinc porphyrin)[60]fullerene in solutions and PMMA films demonstrated strong reverse saturable absorption in Z-scan measurements employing the laser double frequency. The nonlinear absorption coefficient and imaginary part of cubic susceptibility were obtained for solutions and films. The second hyperpolarizability and nonlinear absorption cross section were extracted as well. Penta(zinc porphyrin)[60]fullerene shows attractive optical limiting response property suitable for photonic applications.

Optical limiting properties of hybrid nickel naphthalocyanine-titania nanoparticals thin films

In this work, an ultrathin nanocomposite films containing tetracarboxylic Nickel (Ⅱ) naphthalocyanine (NiNc) and titania nanoparticles are fabricated through electrostatic self-assembled layer-by-layer (LBL) technique. UV–Vis spectroscopy, X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM) are utilized to characterize the film. The optical limiting properties of the composite films are investigated through intensity-dependent transmittance measurements at 600 nm with 18 ps laser pulses. The results show that the composite films have notable optical limiting response (β ∼ 5.4 × 10−7 m/W), which is strongly enhanced compared to both TiO2 and NiNc-only samples. Our results suggest that the nanocomposite films possess the potential for optical limiting applications in the phototherapeutic window.

Optical limiting properties and ultrafast response of three oligomers based on 1,3,5-triazine

Three tri-branched oligomers based on 1,3,5-triazine with large two-photon absorption cross-sections and good optical limiting properties were investigated by UV–Visible, femtosecond Z-scan and one/two-color pump-probe measurements. The two-photon absorption cross-section results measured at a wavelength of 800[Formula: see text]nm were found decreasing with the number of fluorene groups in each branches. The optical limiting properties were also investigated and a two-photon absorption mechanism was proposed. One/two-color pump-probe measurements were also used to further investigate the ultrafast responses of these tri-branched oligomers. The ultrafast response results indicated that after excitation, the tri-branched oligomers will first undergo a fast process to form an intramolecular charge transfer state followed by relaxation of the intramolecular charger transfer state of approximately several hundred ps.

Characterization and enhanced nonlinear optical limiting response in carbon nanodots dispersed in solid-state hybrid organically modified silica gel glasses

Freely dispersed carbon nanodots (CNDs) were introduced into a 3-glycidoxy-propyltrimethoxysilane modified silicate gel glass (i.e. an organically modified silica or ORMOSIL) by a highly efficient and simple sol-gel process, which could be easily extended to prepare functional molecules/nanoparticles solid state optoelectronic devices. Scanning electron microscope imaging, Fourier transform infrared spectroscopy, pore structure measurements, ultraviolet–visible spectroscopy, and fluorescence spectroscopy were used to investigate the surface characteristics, structure, texture, and linear optical properties of the CND/SiO2 ORMOSIL gel glasses. Images and UV/Vis spectra confirmed the successful dispersion of CNDs in the ORMOSIL gel glass. The surface characteristics and pore structure of the host SiO2 matrix were markedly changed through the introduction of the CNDs. The linear optical properties of the guest CNDs were also affected by the sol-gel procedure. The nonlinear optical (NLO) properties of the CNDs were investigated by a nanosecond open-aperture Z-scan technique at 532 nm both in liquid and solid matrices. We found that the NLO response of the CNDs was considerably improved after their incorporation into the ORMOSIL gel glasses. Possible enhancement mechanisms were also explored. The nonlinear extinction coefficient gradually increased while the optical limiting (OL) threshold decreased as the CND doping level was increased. This result suggests that the NLO and OL properties of the composite gel glasses can be optimized by tuning the concentration of CNDs in the gel glass matrix. Our findings show that CND/SiO2 ORMOSIL gel glasses are promising candidates for optical limiters to protect sensitive instruments and human eyes from damage caused by high power lasers.

An all-liquid crystal based high-performance laser protection system via linear/nonlinear dual-mechanisms.

Novel mesogenic [60]fullerenes have been synthesized and doped into cholesteric liquid crystals (CLCs) to achieve a dual-mechanism laser protection system that is effective for both pulsed and broadband cw lasers, simultaneously. It was found that this system integrated a good OPL response, broadband protection range, and high practicability with great potentials in flexible and even wearable protection devices.

Nanosecond nonlinear optical and optical limiting properties of hollow gold nanocages

Gold nanocages (NCs) were prepared using the galvanic replacement reaction. Transmission electron microscopy images confirmed the porous morphology and completely hollow interior of the gold NCs. The nanosecond nonlinear optical and optical limiting (OL) properties of the NCs were characterized using the open-aperture Z-scan technique with 8-ns laser pulses at 532 nm. The gold NCs exhibited intensity-dependent transformation from saturable absorption to reverse-saturable absorption. The nonlinear absorption coefficient and saturable energy of the NCs were 5 × 10− 12 m/W and 2.5 × 1010 W/m2, respectively. Meanwhile, the gold NCs were found to display strong OL properties towards nanosecond laser pulses. The OL threshold of the gold NCs was lower than that of solid gold nanoparticles and comparable with that of a carbon nanotube suspension. Input fluence and angle-dependent scattering measurements indicated that nonlinear scattering plays an important role in the OL behavior of the gold nanostructures at high laser excitation. The improved OL response in gold NCs was discussed from the viewpoint of structural characteristic. The ultrathin and highly porous walls of the gold NCs can effectively transfer the photon-induced heat to the surrounding solvent, resulting in enhanced OL properties compared with those of solid gold nanoparticles. The intensity-dependent transformation from saturable absorption to reverse-saturable absorption and excellent OL response indicate that the smart gold NCs with ultrathin and highly porous walls can be considered as potential candidate in pulse shaping, passive mode locking, and eye protection against powerful lasers.

MoS2 nanosheets covalently functionalized with polyacrylonitrile: synthesis and broadband laser protection performance

Highly soluble polyacrylonitrile (PAN)-covalently grafted MoS2 nanosheets (MoS2–PAN) were synthesized in situ. This material shows superior optical limiting response in the visible and near-infrared ranges.

Electrochemically Organized Isolated Fullerene-Rich Thin Films with Optical Limiting Properties.

Electrochemical assembly was applied directly to determine the aggregation of nanoclusters in isolated fullerene-rich (54-63 wt %) thin films. The electroactive reactions were achieved using electroactive carbazole and pyrene, which led to distinguishable nanoparticle-like and irregular cluster formations. These films, with amorphous and transparent states, showed good photoactivity and significant optical limiting response with an excellent threshold of 63 mJ cm(-2). This work thus paves a way to assemble highly isolated (or monodispersed) building blocks into thin films at the molecular level with control of the nanostructural formations through important molecular design.

Negative thermo-optic coefficients and optical limiting response in pulsed laser deposited Mg-doped ZnO thin films

Thermo-optic properties and optical limiting characteristics are investigated in pulsed laser deposited Mg-doped ZnO thin films by performing a Z-scan experiment in the off-resonant regime using a CW He–Ne laser source. Optical limiting studies in these thin films lead to a conclusion that reverse saturable absorption is the major mechanism for optical limiting properties in these films and nonlinear refraction is caused due to the thermal lensing effect. Negative thermo-optic coefficients were observed, indicating potentiality for athermalization, required to counter the effect of thermal expansion. Sufficiently large thermo-optic coefficients and good optical limiting response suggest the utility of MgZnO films for thermo-optic switches and optical limiting device applications.

Optical limiting response of multi-walled carbon nanotube-phthalocyanine nanocomposite in solution and when in poly (acrylic acid)

Bis{23-(3,4-di-yloxybenzoic acid)-(2(3), 9(10), 16(17), 23(24)-(hexakis-pyridin-3-yloxy phthalocyaninato)} dineodymium (III) acetate (3) is linked to amino-functionalized multi-walled carbon nanotubes (MWCNT) to form 3-MWCNT. Z-scan technique was employed to experimentally determine the nonlinear absorption coefficient from the open-aperture data. The limiting threshold values as low as 0.045 J cm−2 were found in solution. The conjugate (3-MWCNT) gave better optical limiting behavior than complex 3 alone.

Optical Limiting and Theoretical Modelling of Layered Transition Metal Dichalcogenide Nanosheets

Nonlinear optical property of transition metal dichalcogenide (TMDC) nanosheet dispersions, including MoS2, MoSe2, WS2, and WSe2, was performed by using Z-scan technique with ns pulsed laser at 1064 nm and 532 nm. The results demonstrate that the TMDC dispersions exhibit significant optical limiting response at 1064 nm due to nonlinear scattering, in contrast to the combined effect of both saturable absorption and nonlinear scattering at 532 nm. Selenium compounds show better optical limiting performance than that of the sulfides in the near infrared. A liquid dispersion system based theoretical modelling is proposed to estimate the number density of the nanosheet dispersions, the relationship between incident laser fluence and the size of the laser generated micro-bubbles, and hence the Mie scattering-induced broadband optical limiting behavior in the TMDC dispersions.

Nonlinear Scattering and Absorption Effects in Size-Selected Diphenylpolyynes

The nonlinear optical properties of monodispersed diphenylpolyynes with different chain length were studied by using a nanosecond pulsed laser excitation. A strong optical limiting response was detected at laser fluences above 0.35 J/cm2. The nature of the nonlinear effect as a function of the number of carbon atoms in the linear chain was investigated by the Z-scan technique, determining the molecular second-order hyperpolarizability γ. An interesting coupling was found between the decrease of scattering phenomena and the alignment of longer carbon chains in the focus region. The effect of an external highly intense electric field, combined with a detailed density functional theory (DFT) investigation, has been invoked to explain molecular arrangement, polarizability, isomery, and scattering of diphenylpolyynes. The interesting findings derived from our investigations demonstrate that phenyl-end-capped polyynes could be very interesting for various optoelectronic applications.

Poly(9,9′‐diheylfluorene carbazole) Functionalized with Reduced Graphene Oxide: Convenient Synthesis using Nitrogen‐Based Nucleophiles and Potential Applications in Optical Limiting

Covalently functionalized reduced graphene oxide (RGO) sheet was prepared by treating nitrogen-centered anions generated from poly(9,9'-diheylfluorene carbazole) (PCF) with GO. The resultant hybrids with different chemical behavior were separated by centrifugation. The covalent modification was fully characterized by IR spectroscopy, UV/Vis spectroscopy, thermogravimetric analysis (TGA), Raman spectroscopy, TEM, and SEM. It was found that RGO-PCF-s, the soluble part, was split into small platelets with a size of about 200 nm, and the hydrophobic polymer PCF became hydrophilic after wrapping by RGO. The content of RGO in RGO-PCF-s was about 11.9%, and the hybrid material showed good dispersion stability in water. Besides, RGO-PCF-i, the insoluble part, with larger size, displayed excellent optical-limiting response, in which both nonlinear absorption and nonlinear scattering play important roles. As nitrogen-centered anions are an important type of intermediates in chemistry, this one-step "grafting-to" strategy could be used to obtain RGO-based materials with different applications.