Nonlinear optical properties of Cu nanocluster composite fabricated by 180 keV ion implantation

Metal nanocluster composite glass prepared by 180 keV Cu ions into silica with dose of 5×10¹⁶ ions/cm² has been studied. The microstructural properties of the nanoclusters has been verified by optical absorption spectra and transmission electron microscopy (TEM). Third-order nonlinear optical properties of the nanoclusters were measured at 1064 and 532 nm excitations using Z-scan technique. The nonlinear refraction index, nonlinear absorption coefficient, and the real and imaginary parts of the third-order nonlinear susceptibility were deduced. Results of the investigation of nonlinear refraction by the off-axis Z-scan configuration were presented and the mechanisms responsible for the nonlinear response were discussed. Third-order nonlinear susceptibility χ⁽³⁾ of this kind of sample was determined to be 8.7×10⁻⁸ esu at 532 nm and 6.0×10⁻⁸ esu at 1064 nm, respectively.     

Nonlinear optical properties of Au/ZnO nanoparticle arrays

The triangular-shaped Au/ZnO nanoparticle arrays were fabricated on fused quartz substrate using nanosphere lithography. The structural characterization of the Au/ZnO nanoparticle arrays was investigated by atomic force microscopy. The absorption peak due to the surface plasmon resonance of Au particles at the wavelength of about 570 nm was observed. The nonlinear optical properties of the nanoparticle arrays were measured using the z-scan method at a wavelength of 532 nm with pulse duration of 10 ns. The real and imaginary part of third-order nonlinear optical susceptibility, Re χ⁽³⁾ and Im χ⁽³⁾, were determined to be 1.15 × 10⁻⁶ and −5.36 × 10⁻⁷ esu, respectively. The results show that the Au/ZnO nanoparticle arrays have great potential for future optical devices.     

Third-order optical nonlinearity of (Ba0.7Sr0.3)TiO3 ferroelectric thin films fabricated by soft solution processing

(Ba_0.7Sr_0.3)TiO₃ (BST) ferroelectric thin films with perovskite crystal structure were fabricated by soft solution processing on a quartz substrate. The third-order nonlinear optical properties were investigated by using Z-scan technique. Positive nonlinear refractive index and nonlinear absorption coefficient were determined to be 4×10⁻⁷ esu and 1.2×10⁻⁶ m/w, respectively. The real part and imaginary part of third-order optical nonlinear susceptibility were calculated and the values were 6.43×10⁻⁸ and 5.14×10⁻⁸ esu, respectively. All of these results show ferroelectric BST thin film is promising for applications in nonlinear optical devices.     

Third-order nonlinear optical properties of multiwalled carbon nanotubes modified by CdS nanoparticles

CdS nanoparticles were coated on the side wall of multiwalled carbon nanotubes (MWCNTs) by a wet chemical synthesis approach via noncovalent functionalization of MWCNTs with poly(diallyldimethylammonium chloride) (PDDA). The as-prepared material was characterized by X-ray diffraction (XRD), UV–vis absorption, fluorescence and transmission electron microscopy (TEM). The results indicated that CdS nanoparticles were uniformly coated on the surface of MWCNTs. Third-order optical nonlinearity of the as-prepared material was studied with the Z-scan technique with picosecond laser pulses at 532 nm. The Z-scan curve revealed that CdS nanoparticle-modified MWCNTs exhibited negative nonlinear refraction index and positive absorption coefficient. The real part and imaginary part of the third-order nonlinear susceptibility χ⁽³⁾ were calculated to be −4.9 × 10⁻¹² and 6.8 × 10⁻¹³ esu, respectively.     

Nonlinear optical studies of 1-3-diaryl-propenones containing 4-methylthiophenyl moieties

The third-order nonlinear optical properties of chalcone derivatives have been studied using the single beam Z-scan technique. The dependence of χ⁽³⁾ on different donor and acceptor type substituents demonstrates the electronic nonlinearity of compounds. The largest value of nonlinear refractive index, n₂, measured for a high electron donor substituted molecule is −2.033 × 10⁻¹¹ esu. These molecules exhibit a strong two-photon absorption and interesting optical limiting of nanosecond laser pulses at 532 nm.     

Single beam Z-scan measurement of the third order optical nonlinearities of styryl7 dye

The optical nonlinearity of styryl7 dye in ethanol solution at different concentrations has been studied using pulsed Nd:YAG laser at 532 nm as the source of excitation. The optical responses were characterized by measuring the intensity dependent refractive index (n₂) of the medium using the Z-scan technique. The open aperture Z-scan trace of the dye in solution displayed saturable absorption. The closed aperture Z-scan trace of the dye exhibited a negative nonlinearity. The styryl7 dye at 1 mM concentration exhibited nonlinear refractive co-efficient n₂ = −1.24 × 10⁻⁸ cm²/W, nonlinear absorption coefficient β = − 3.9 × 10⁻⁴ cm/W and real and imaginary parts of third-order nonlinear optical susceptibility χ³ = 3.26 × 10⁻⁶ esu in ethanol. These results showed that the dye has potential application in nonlinear optics.     

Photophysical and nonlinear optical properties of an azobenzene substituted zinc phthalocyanine

Photophysical property and third-order optical nonlinearity of an azobenzene substituted zinc phthalocyanine (azo-ZnPc) in chloroform solution were studied by UV–Vis spectra method and a picosecond Z-scan technique at 532 nm with pulse duration of 25 ps, respectively. It was found that the azo-ZnPc shows large positive nonlinear refraction and positive nonlinear absorption, exhibiting the defocusing effect and reverse saturable absorption, respectively. The molecular second hyperpolarizability of the azo-ZnPc dyad was measured to be 3.9 × 10⁻³⁰ esu. All the results suggest that the studied azo-ZnPc dyad may have potential applications in the field of nonlinear optics.     

Nonlinear optical studies of a newly synthesized copolymer containing oxadiazole and substituted thiophenes

We investigated the third-order nonlinear optical properties of a newly synthesized soluble copolymer containing oxadiazole and thiophene units using Z-scan and Degenerate Four Wave Mixing (DFWM) techniques. The measurements were performed at 532 nm with 7 ns pulses from a Nd:YAG laser. We found a good agreement between the values of χ⁽³⁾ determined from both experiments. Z-scan results indicate a negative nonlinear refractive index, n₂, whose magnitude is of the order of 10⁻¹⁰ esu. The copolymer exhibits strong nonlinear absorption and good optical limiting properties at 532 nm, and hence may be a potential material for optical limiting applications.     

Femtosecond Z-scan measurement of third-order optical nonlinearities in anatase TiO2 thin films

Anatase phase TiO₂ films have been grown on fused silica substrate by pulsed laser deposition technique at substrate temperature of 750 °C under the oxygen pressure of 5 Pa. From the transmission spectra, the optical band gap and linear refractive index of the TiO₂ films were determined. The third-order optical nonlinearities of the films were measured by Z-scan method using a femtosecond laser (50 fs) at the wavelength of 800 nm. The real and imaginary parts of third-order nonlinear susceptibility χ⁽³⁾ were determined to be −7.1 × 10⁻¹¹esu and −4.42 × 10⁻¹²esu, respectively. The figure of merit, T, defined by T=βλ/n₂, was calculated to be 0.8, which meets the requirement of all-optical switching devices. The results show that the anatase TiO₂ films have great potential applications for nonlinear optical devices.     

χ measurement and optical limiting studies of urea picrate

The molecular charge complex urea picrate (UP) was synthesized and its third order nonlinear optical properties have been investigated using a single beam Z-scan technique with nanosecond laser pulses at 532 nm. Open aperture data of the compound indicates two photon absorption at this wavelength. The nonlinear refractive index n₂, nonlinear absorption coefficient β, magnitude of effective third order susceptibility χ⁽³⁾, the second order hyperpolarizability γ_h and the coupling factor ρ have been estimated. The experimentally determined values of β, n₂, Re χ⁽³⁾ and Im χ⁽³⁾, γ_h and ρ of the compound UP are 2.146 cm/GW, −1.258×10⁻¹¹ esu, −1.347×10⁻¹³ esu, 0.377×10⁻¹³ esu, 0.69×10⁻³² esu and 0.28, respectively. The compound exhibits good optical limiting at 532 nm with the limiting threshold of 80 μJ/pulse. Our studies suggest that compound UP is a potential candidate for optical device applications such as optical limiters.     

3,3′-Benzene-1,4-diylbis[1-(substituted)phenylprop-2-en-1-one] derivatives: A new class of materials for third-order nonlinear optical applications

We have investigated the third-order nonlinear optical parameters of Bischalcones embedded in DMF solution and in solid PMMA matrix, by Z-scan technique using nanosecond laser pulse trains at 532 nm. Z-scan results reveal that the Bischalcones exhibits negative nonlinear refractive index as high as 10⁻¹¹ esu. The molecular two-photon absorption cross-section of Bischalcones were of the order 10⁻⁴⁶ cm⁴ s/photon, which is nearly two orders of magnitude larger than that of Rhodamine 6G which is 10⁻⁴⁸ - 10⁻⁵⁰ cm⁴ s/photon. We found that, the two-photon absorption (TPA) is the dominating nonlinear process leading to nonlinear absorption in both the cases in solution and as well as in solid medium. Based on TPA process, the Bischalcones exhibit good optical power limiting of nanosecond laser pulses at the input wavelength. The nonlinear optical parameters found to increase on enhancing the strength of the electron donor groups indicating the dependence and importance of electron donor/acceptor units on third-order nonlinear optical susceptibility χ⁽³⁾.     

Te/TeO2-SiO2复合薄膜的吸收和非线性光学特性研究

应用分光光度计测量Te/TeO₂-SiO₂复合薄膜的透射光谱和吸收光谱, 在480nm附近观察到Te颗粒引起的等离子体共振吸收峰; 采用Z扫描技术研究了共振(激发波长为532 nm)和非共振情况下(激发波长1064 nm) 不同电位制备薄膜的Te颗粒状态与复合薄膜的三阶非线性极化率的关系. 基于有效介质理论对复合薄膜的三阶非线性效应进行分析, 研究Te颗粒大小对Te/TeO₂-SiO₂复合薄膜的非线性光学性质的影响及其产生机理. 结果表明薄膜制备过电位增大, Te的粒径减小, 颗粒数量多, 颗粒分布趋于均匀, 使得金属颗粒的表面等离子体共振峰红移, 吸收强度增强, 导致三阶非线性光学效应增强, χ⁽³⁾由1064 nm的5.12×10^-7 esu增大为532 nm的8.11×10^-7 esu. 关键词： 碲 二氧化碲 复合薄膜 三阶非线性     

CdSe量子点的线性和非线性光学特性

主要从实验和理论两个方面,探讨了强受限尺寸区域内不同尺寸对CdSe量子点线性和非线性光学性质的影响.用吸收光谱研究了量子点尺寸与吸收峰之间的关系,用皮秒Z扫描技术研究了共振和非共振情况下(激发光波长分别为532和1064nm),尺寸与三阶非线性极化率之间的关系.基于电子能量状态理论和局域场增强理论对量子点进行分析,得到了CdSe不同尺寸的三阶非线性效应,研究了尺寸对量子点非线性光学性质的影响.结果表明,由激发态粒子数布局改变和纳米颗粒增大引起的非线性共振增强效应相当,二者共同作用使得三阶极化率增强20倍左右,且用532nm的共振频率激发4.3nm CdSe量子点时,χ⁽³⁾具有最大值2.0×10^-11esu. 关键词： CdSe量子点 三阶非线性 Z扫描')" href="#">Z扫描 量子限域效应     

Third-order nonlinear optical studies of new anthraquinone derivatives

Four new donor-acceptor-donor anthraquinone derivatives were synthesized and characterized by UV, IR, ¹H NMR and elemental analysis. Their off-resonant third-order nonlinear optical properties were measured using femtosecond laser and degenerate four-wave mixing technique. The third-order nonlinear optical susceptibilities χ⁽³⁾ were 3.36-3.76 × 10⁻¹³ esu. The nonlinear refractive indexes n₂ were 6.19-6.91 × 10⁻¹² esu. The second-order hyperpolarizabilities γ of the molecules were 3.36-3.76 × 10⁻³¹ esu. The response times were 101-115 fs. The results show that these compounds have potential nonlinear optical applications.     

Nonlinear optical properties of periodic gold nanoparticle arrays

Periodic Au nanoparticle arrays were fabricated on silica substrates using nanosphere lithography. The identical single-layer masks were prepared by self-assembly of polystyrene nanospheres with radius R = 350 nm. The structural characterization of nanosphere masks and periodic particle arrays was investigated by atomic force microscopy. The nonlinear optical properties of the Au nanoparticle arrays were determined using a single beam z-scan method at a wavelength of 532 nm with laser duration of 55 ps. The results show that periodic Au nanoparticle arrays exhibit a fast third-order nonlinear optical response with the nonlinear refractive index and nonlinear absorption coefficient being n₂ = 6.09 × 10⁻⁶ cm²/kW and β = −1.87 × 10⁻⁶ m/W, respectively.     

The nonlinear optical response of new organometallic compounds under picosecond excitation

The nonlinear optical response of three new organometallic compounds was studied by z-scan method under picosecond excitation at 1064 and 532 nm. The compounds showed self-focus effect at both wavelengths, and effective reverse saturation absorption at 532 nm and strong two-photon absorption at 1064 nm occurred. Through calculating and comparing the nonlinear optical indexes of the compounds, we found that the third-order nonlinear susceptibility was enhanced by two-fold for one photon transition resonant effect, and incorporating different heavy metal atoms in the delocalized organic system slightly influenced the nonlinear optical indexes.     

Third-order nonlinear optical properties of thin sputtered gold films

Au films of thickness ranging between 5 and 52 nm were prepared by sputtering on quartz substrates and their third-order nonlinear optical response was investigated by Optical Kerr effect (OKE) and Z-scan techniques using 532 nm, 35 ps laser pulses. All prepared films were characterized by XRD, AFM and UV-VIS-NIR spectrophotometry while their third-order susceptibility χ⁽³⁾ was measured and found to be of the order of 10⁻⁹ esu. The real and imaginary parts of the third-order susceptibility were found in very good agreement with experimental results and theoretical predictions reported by Smith et al. [D.D. Smith, Y. Yoon, R.W. Boyd, Y.K. Cambell, L.A. Baker, R.M. Crooks, M. George, J. Appl. Phys. 86 (1999) 6200].     

Third-order nonlinear optical response of newly synthesized accepter/donor substituted propylidene aryloxy acet hydrazide

A class of organic compounds namely propylidene aryloxy acet hydrazide derivatives were synthesized. The third-order nonlinear optical properties and optical limiting studies of the compounds were investigated using the single beam Z-scan technique at 532 nm. The Z-scan study reveals that the compounds exhibit a self-defocusing effect at 532 nm. The calculated values of nonlinear refractive index, third-order nonlinear optical susceptibility and second order molecular hyperpolarizability are of the order of 10^?11 esu, 10^?13 esu and 10^?31 esu, respectively. The compounds exhibit good optical limiting properties at the wavelength used.     

Anisotropic nonlinear optical absorption of gold nanorods in a silica matrix

Nanocomposite films consisting of gold nanospheres or gold nanorods embedded in a silica matrix have been prepared using a hybrid deposition technique consisting of plasma-enhanced chemical vapor deposition of SiO₂ and co-sputtering of gold, followed by annealing at 900 °C. Subsequent irradiation with 30 MeV heavy ions (Cu⁵⁺) was used to form gold nanorods. Linear and nonlinear optical properties of this material are closely related with the surface plasmon resonance in the visible. The nonlinear absorption coefficient (α₂@532 nm) for the films containing gold nanospheres was measured by Z-scan and P-scan techniques, and it was found to be isotropic and equal to −4.8 × 10⁻² cm/W. On the contrary, gold nanorods films exhibited two distinct surface plasmon resonance absorption bands giving rise to a strong anisotropic behavior, namely a polarization-dependent linear absorption and saturable absorption. Z-scan and P-scan measurements using various light polarization directions yielded nonlinear absorption coefficient (α₂@532 nm) values varying from −0.9 × 10⁻² cm/W up to −3.0 × 10⁻² cm/W. Linearity of the P-scan method in the context of nanocomposite saturable absorption is also discussed.     

The nonlinear refraction and nonlinear absorption in 4-(4,6-diaminopyrimidin-2-ylthio) substituted double-decker Lu(III) phthalocyanine

A 4-(4,6-diaminopyrimidin-2-ylthio) substituted double-decker Lu(III) phthalocyanines (4) have been prepared and characterized by elemental analysis, IR, UV-vis and ¹H NMR spectroscopies. The nonlinear refractive index, nonlinear absorption and the optical limiting (OL) performance of the compound 4 in a 0.5 mm spectroscopic cell in DMF solution were investigated by using 4 ns pulse laser at 532 nm. Z-scan experiments have been conducted between 0.24 and 2.39 GW/cm² peak intensities for 10 Hz repetition rate and also between 2.39 and 23.89 GW/cm² peak intensities for 1 Hz repetition rate. The thermal effect contributes to the nonlinear response of the material higher than 0.72 GW/cm² peak intensity at 10 Hz. We measured the effective nonlinear refractive index of the material as 1.2×10⁻¹¹ esu at 3.5×10⁻⁴ M concentration with the peak intensity less than 0.72 GW/cm² and we found that nonlinear absorption was very small. On the other hand, when concentration is increased to 2.4×10⁻³ M material's nonlinear absorption becomes dominant mechanism for the nonlinear response and the compound 4 indicates OL behavior at 2.4×10⁻³ M concentration.