Tuning the nonlinear optical absorption of reduced graphene oxide by chemical reduction.

Reduced graphene oxides with varying degrees of reduction have been produced by hydrazine reduction of graphene oxide. The linear and nonlinear optical properties of both graphene oxide as well as the reduced graphene oxides have been measured by single beam Z-scan measurement in the picosecond region. The results reveal both saturable absorption and two-photon absorption, strongly dependent on the intensity of the pump pulse: saturable absorption occurs at lower pump pulse intensity (~1.5 GW/cm2 saturation intensity) whereas two-photon absorption dominates at higher intensities (≥5.7 GW/cm2). Intriguingly, we find that the two-photon absorption coefficient (from 1.5 cm/GW to 4.5cm/GW) and the saturation intensity (from 1 GW/cm2 to 2 GW/cm2) vary with chemical reduction, which is ascribed to the varying concentrations of sp2 domains and sp2 clusters in the reduced graphene oxides. Our results not only provide an insight into the evolution of the nonlinear optical coefficient in reduced graphene oxide, but also suggest that chemical engineering techniques may usefully be applied to tune the nonlinear optical properties of various nano-materials, including atomically thick graphene sheets.

The effect of overall parental satisfaction on Chinese students' learning engagement: Role of student anxiety and educational implications.

Learning engagement is one of the important research contents of learning psychology. The level of learning engagement directly affects students' academic performance and future development. Based on the survey data of primary and secondary school parents and students collated at the beginning of 2019, control factors such as students' gender, school location, parents' education level, total annual family income, parental rearing methods, etc. The study found that parental overall satisfaction can significantly and positively predict students' learning engagement. Mediation effect analysis found that students' anxiety completely mediated the effect on parental overall satisfaction and students' learning engagement. Cultivate good parent-child relationships; Establish positive teacher-student relationships; Build a harmonious relationship with classmates. Families and schools should work together to create an atmosphere conducive to the healthy growth of students.

Research on online teachers' training based on the gamification design: A survey analysis of primary and secondary school teachers.

The current form of teacher education and training has gradually shifted to distance training, but the most prominent performance of the participants in network training is the lack of motivation and enthusiasm for participation, and the participants participate in the training with the mentality of coping with the assessment, and the training effect is naturally not very good. At this point, the concept of gamification learning has become popular. Gamification applies game thinking and mechanics to non-game areas to guide user interaction and use. Based on Professor Kevin Werbach's gamification design framework, this study developed a case study of gamification for online teacher training, implemented in a professional development program for primary and secondary school teachers in Zhejiang Province, China. A self-administered questionnaire was then surveyed in three teaching classes, and the results found that: Firstly The participants' satisfaction in response to the gamification case was at a moderate to high level (M > 4.0, Tot = 5.0); Secondly, demographic factors did not significantly influence this (p > 0.05); Thirdly, among the gamification design influencing factors, presentation and feedback were the most influential (b = 0.536,p = 0.000), goals and rules (b = 0.167, p = 0.012), communication and interaction (b = 0.155, p = 0.029), and personalization (b = 0.154, p = 0.020) in decreasing order; Fourthly, The effect of case implementation significantly impacted participants' intention to sustain participation (b = 0.874, p = 0.000). Finally, we distilled the study's shortcomings and the prospects for future research.

Silver nanoparticles grown in organic solvent PGMEA by pulsed laser ablation and their nonlinear optical properties.

Well dispersed silver nanoparticles (AgNPs) with narrow size distribution have been grown in organic solvent propylene glycol monomethyl ether acetate (PGMEA) by pulsed laser ablation techniques. The presence of AgNPs in PGMEA solvent gives rise to an enhancement of the absorption and nonlinear optical properties due to the surface plasmon resonance induced by AgNPs. The shape and density of the AgNPs have been estimated by fitting the absorption spectra with a given model, and the results also show that an additional laser irradiation treatment can improve the monodispersity of the AgNPs and their nonlinear optical properties. The synthesis of AgNPs in PGMEA will facilitate adding AgNPs into organic functional materials especially for photoresist to modify their optical properties.

Parents' Educational Anxiety Under the "Double Reduction" Policy Based on the Family and Students' Personal Factors.

Introduction: Educational anxiety is a true portrayal of Chinese parents. As an endogenous problem in the development of modern education system, the pressure of students' entrance examination continues to rise. Methods: Based on the empirical survey data of education in 3298 families, this study uses the analysis method of multiple linear regressions to analyze the influencing factors of parental education anxiety and finds that educational anxiety has become a common social emotion. Results: After the regression analysis of the four-layer model was established, it was found that different school segments, school priorities, and student achievements had a significant impact on parents' educational anxiety, and factors such as annual family income, educational satisfaction and family parenting style had a significant impact on parental educational anxiety. It is worth noting that the gap in parental expectations has a significant positive effect on educational anxiety, and the greater the expectation gap, the higher the educational anxiety of parents. Discussion: Therefore, it is suggested that governments at all levels should conscientiously implement the task of "reducing burdens" and rationally allocate high-quality educational resources; parents and teachers should start from the needs of children to establish a scientific concept of education and the concept of becoming a talent; the whole society should put forward reasonable educational expectations in education, and be good at adjusting expectations on time so that education can return to a rational natural growth state and eliminate parents' educational anxiety.

Pre-service teachers' emotional experience: Characteristics, dynamics and sources amid the teaching practicum.

Recently, teacher emotions have become the focus of research in teacher education. Teacher emotions not only affect teachers themselves but also have an impact on their students. However, pre-service teachers' emotions have been neglected. This study is based on a qualitative analysis of online emotional diaries related to emotional experience expression by 120 Chinese pre-service teachers before, during, and after teaching practice. The results in this study show three characteristics of pre-service teachers' emotional experiences: the overall positive emotions are higher than negative emotions; "caring" and "nervous" are the most typical emotions and variability in emotional experience across gender and internship schools. Then, it is surprising that pre-service teachers' emotional trajectories are complex and dynamic, positive emotions are decreasing, and negative emotions increase as time goes by. Finally, from the perspective of emotional experience sources, organizational factors affect the emotional experience, personal factors, and background factors.

Third-order optical nonlinearity of gold nanoparticle arrays embedded in a BaTiO3 matrix.

Au:BaTiO(3) composite films comprising hexagon-shaped Au nanoparticle arrays covered with BaTiO(3) matrix were fabricated by double-layer nanosphere lithography and pulsed laser deposition technique. The optical nonlinearity of the composite film was determined using the Z-scan technique at a wavelength of 532 nm and a pulse duration of 25 ps. The third-order nonlinear optical susceptibility, chi(3), was found to be 2.9x10(-8) esu, which is comparable with the best values in metal-dielectric films comprising randomly distributed spherical particles but with much higher metal concentrations. The local electric field enhancement in and near the particles was investigated using the dipole discrete approximation method.

All-optical switching in subwavelength metallic grating structure containing nonlinear optical materials.

All-optical switching based on a subwavelength metallic grating structure containing nonlinear optical materials has been proposed and numerically investigated. Metal-dielectric composite material is used in the switching for its larger third-order nonlinear susceptibility (approximately 10(-7)esu) and ultrafast response properties. The calculated dependence of the signal light intensity on the pump light intensity shows a bistable behavior, which results in a significant switch effect. It rests on a surface plasmon's enhanced intensity-dependent change of the effective dielectric constant of Kerr nonlinear media, corresponding to a transition of the far-field transmission from a low- to high-transmission state. The study of this switching structure shows great advantages of smaller size, lower requirement of pump light intensity, and shorter switching time at approximately the picosecond level.

Enhancement of optical nonlinearity in periodic gold nanoparticle arrays.

Linear and nonlinear optical properties of periodic triangular Au nanoparticle arrays were investigated. We compared the optical nonlinearity of periodic Au nanoparticle arrays with that of the ultra-thin gold film consisting of randomly distributed spheroidal clusters. A pronounced enhancement of the third-order nonlinear optical susceptibility χ((3)) in Au arrays was observed, and the figure of merit, χ((3))/α, of the periodic nanoparticle arrays is one order of magnitude larger than that of the ultra-thin film. Such an enhancement of the optical nonlinearity could be due to the strong local field near the triangular nanoparticles.

Nonlinear refraction and saturable absorption in Au:BaTiO3 composite films.

Composite thin films Au:BaTiO3, comprising nanometer-sized gold particles embedded in barium titanate matrices, were synthesized on MgO (100) substrates with the pulsed laser deposition technique. The nanostructure of the films and the size distributions of the Au particles were analyzed by high-resolution transmission electron microscopy. Crystal lattice fringes from the Au nanocrystals and the BaTiO3 matrices were observed. The nonlinear optical properties of the Au:BaTiO3 films were measured with the z-scan method at a wavelength of 532 nm, which was closed to the surface plasmon resonance of nanoscale Au particles. The features of the closed-aperture z-scan transmittance curves were affected by the ratio, which increased greatly at a high metal concentration, of the imaginary part to the real part of the third-order nonlinear susceptibility chi(3).

Rh:BaTiO3 thin films with large nonlinear optical properties.

We report the fabrication and the nonlinear optical properties of Rh-doped BaTiO3 thin films. The films were deposited on SrTiO3 (100) substrates by pulsed-laser deposition. The deposited Rh:BaTiO3 thin films were single phase and c-axis orientation investigated by x-ray diffraction. The films exhibited large nonlinear optical effects, which were determined using Z-scan technique at a wavelength of 532 nm with a laser duration of 10 ns. The real and imaginary parts of the third-order nonlinear susceptibility chi (3) were 5.71 x 10(-7) esu and 9.59 x 10(-8) esu, respectively. The value of Re chi (3) of Rh:BaTiO3 films is much larger than those of several representative nonlinear optical thin films. The results show that Rh:BaTiO3 thin films have great potential applications for nonlinear optical devices.