How data knowledge transformation affects teachers' precision teaching ability: The mediating effect of data consciousness.

With the development of smart education, teachers' precision teaching ability has increasingly become an important component of their professional ability. Based on the Socialization, Externalization, Combination, Internalization (SECI) model of knowledge management, this research constructs a theoretical model of data knowledge transformation, data consciousness, and teachers' precision teaching ability, and uses Partial Least Squares to analyze the interaction and influence among the elements. The empirical results show that the transformation of internal knowledge related to data has a significant positive impact on the improvement of teachers' precision teaching ability and data consciousness; the transformation of external knowledge related to teaching has a positive effect on the teaching management ability of teachers' precision teaching ability, but the effect is not significant. Data consciousness plays a partial mediating effect between internal knowledge transformation and teachers' precision teaching ability, and a complete mediating effect between external knowledge transformation and teaching management ability.

Second-harmonic generation of single-mode Laguerre-Gaussian beams with an improved quasi-phase-matching method.

In the second-harmonic generation processes involving Laguerre-Gaussian (LG) beams, the generated second-harmonic wave is generally composed of multiple modes with different radial quantum numbers. To generate single-mode second-harmonic LG beams, a type of improved quasi-phase-matching method is proposed. The Gouy phase shift has been considered in the optical superlattice designing and an adjustment phase item is introduced. By changing the structure parameters, each target mode can be phase-matched selectively, whose purity can reach up to 95%. The single LG mode generated from the optical superlattice can be modulated separately and used as the input signals in the mode division multiplexing system.

Switchable Electromagnetically Induced Transparency with Toroidal Mode in a Graphene-Loaded All-Dielectric Metasurface.

Active photonics based on graphene has attracted wide attention for developing tunable and compact optical devices with excellent performances. In this paper, the dynamic manipulation of electromagnetically induced transparency (EIT) with high quality factors (Q-factors) is realized in the optical telecommunication range via the graphene-loaded all-dielectric metasurface. The all-dielectric metasurface is composed of split Si nanocuboids, and high Q-factor EIT resonance stems from the destructive interference between the toroidal dipole resonance and the magnetic dipole resonance. As graphene is integrated on the all-dielectric metasurface, the modulation of the EIT window is realized by tuning the Fermi level of graphene, engendering an appreciable modulation depth of 88%. Moreover, the group velocity can be tuned from c/1120 to c/3390. Our proposed metasurface has the potential for optical filters, modulators, and switches.

Compact terahertz spectrometer based on sequential modulation of disordered rough surfaces.

We present herein a compact terahertz (THz) spectrometer in which transmission intensity distribution associated with dispersive interference effects in disordered random surfaces are used for reconstructing the frequency contents of an incoming THz beam. The device sweeps the frequency-dependent parameter of a roughened transmission plate through lateral displacement or electro-optic modulation. 2D transmission intensities are sequentially captured by a single detector for a range of modulation depths. With a calibration data set as the reference, one can reconstruct the spectra of the probe THz beam by solving a system of simultaneous linear equations. A smoothing Tikhonov regularization approach has been implemented to improve the accuracy of the spectral reconstruction. The reported compact, broadband, high-resolution THz spectrometer is well suited for portable THz spectroscopy applications.

Nearly Diffraction-Free Nonlinear Imaging of Irregularly Distributed Ferroelectric Domains.

Second-harmonic generation is used experimentally for the nonlinear imaging of two-dimensional irregular domain structures. Analytical solutions and simulation results for the Fresnel distribution of domain walls are obtained. The results show that the domain wall plays an important role in the imaging process and the corresponding diffraction effect is greatly suppressed (we call it a nearly diffraction-free effect), thus providing a simple way to realize high-resolution imaging for ferroelectric domains.

Time-reversed and reciprocal second-harmonic generation with pump depletion.

The time-reversed second-harmonic generation in one-dimensional nonlinear photonic crystals has been theoretically studied without the undepleted pump approximation. A simple criterion has been deduced which determines the energy flow. Based on it, two kinds of structures with different symmetries are presented to realize the nonlinear time reversal effect. A completely reciprocal nonlinear response is also found in the same process. Furthermore, a multi-section-cascaded structure is proposed to realize the nonlinear time reversal at any given position.

Q-factor enhancement of Fano resonance in all-dielectric metasurfaces by modulating meta-atom interactions.

We numerically investigated the effects of meta-atom interactions on the Fano resonance in all-dielectric metasurfaces by introducing alternately flipped asymmetric paired bars (APBs) and split asymmetric paired bars (SAPBs). With alternately flipped configurations, the Q-factor of the Fano resonance is significantly enhanced up to one order of magnitude, and the electric field is strengthened by more than twice. Abnormally, the Q-factor increases with gap size in the alternately flipped SAPBs. These are attributed to the destructive interaction among nearest-neighbor dipole resonators. The Q-factor of 108 and Raman enhancement factor of 109 in the gap can be realized with the alternately flipped SAPBs made of Si. Our study provides a way to improve performance of practical devices such as ultrasensitive sensors, nonlinear optics, and quantum emitters.

Analytical investigation of nonreciprocal response in 1D nonlinear photonic crystals.

The nonreciprocal response of the SHG process in 1D periodical nonlinear photonic crystals with a defect embedded has been theoretically studied by solving the nonlinear coupled equations. The nonreciprocal response has been deduced analytically with the solution of non-reciprocity parameters obtained. The result shows that as the non-reciprocity approaches 100%, the crystal length and the input power needed increase at a logarithmic rate. Any target nonreciprocal response can be reached in this structure by adjusting the structure parameters.

The conflicting role of buckled structure in phonon transport of 2D group-IV and group-V materials.

Controlling heat transport through material design is one important step toward thermal management in 2D materials. To control heat transport, a comprehensive understanding of how structure influences heat transport is required. It has been argued that a buckled structure is able to suppress heat transport by increasing the flexural phonon scattering. Using a first principles approach, we calculate the lattice thermal conductivity of 2D mono-elemental materials with a buckled structure. Somewhat counterintuitively, we find that although 2D group-V materials have a larger mass and higher buckling height than their group-IV counterparts, the calculated κ of blue phosphorene (106.6 W mK-1) is nearly four times higher than that of silicene (28.3 W mK-1), while arsenene (37.8 W mK-1) is more than fifteen times higher than germanene (2.4 W mK-1). We report for the first time that a buckled structure has three conflicting effects: (i) increasing the Debye temperature by increasing the overlap of the pz orbitals, (ii) suppressing the acoustic-optical scattering by forming an acoustic-optical gap, and (iii) increasing the flexural phonon scattering. The former two, corresponding to the harmonic phonon part, tend to enhance κ, while the last one, corresponding to the anharmonic part, suppresses it. This relationship between the buckled structure and phonon behaviour provides insight into how to control heat transport in 2D materials.

Giant circular dichroism and its reversal in solid and inverse plasmonic gammadion-shaped structures.

Chiral plasmonic structures have been shown to possess large circular dichroism (CD) responses. Here, we investigate the CD responses in a solid and inverse metallic structure composed of a stacked right-twisted gammadion metallic nanoparticle and a left-twisted gammadion nanoaperture array, where a giant circular dichroism is achieved. In addition, the sign of the CD responses can be reversed through the changes of the geometric parameters. Further analysis reveals that the Fabry-Perot (F-P) resonance of cross-polarization conversion of electric field governs the change of the CD. It can be envisioned that our findings will allow further tuning and manipulation of the CD responses for tailored circular polarized light-matter interaction.

Theoretical study on the Cerenkov-type second-harmonic generation in optical superlattices without paraxial approximation.

In this paper, the Cerenkov-type second-harmonic generation in bulk optical superlattices has been studied theoretically with the non-paraxial wave equations, where the paraxial approximation is avoided. The corresponding phase-matching condition is determined strictly by solving the non-paraxial wave equations under proper boundary conditions, and the result coincides well with the traditional Cerenkov phase-matching condition. In addition, a backward Cerenkov phase-matching condition is deduced from the wave equations as well, and the physical requirement of this condition is clarified.

2D wave-front shaping in optical superlattices using nonlinear volume holography.

Nonlinear volume holography is employed to realize arbitrary wave-front shaping during nonlinear processes with properly designed 2D optical superlattices. The concept of a nonlinear polarization wave in nonlinear volume holography is investigated. The holographic imaging of irregular patterns was performed using 2D LiTaO3 crystals with fundamental wave propagating along the spontaneous polarization direction, and the results agree well with the theoretical predictions. This Letter not only extends the application area of optical superlattices, but also offers an efficient method for wave-front shaping technology.

From Ewald sphere to Ewald shell in nonlinear optics.

Ewald sphere is a simple vector scheme to depict the X-ray Bragg diffraction in a crystal. A similar method, known as the nonlinear Ewald sphere, was employed to illustrate optical frequency conversion processes. We extend the nonlinear Ewald sphere to the Ewald shell construction. With the Ewald shell, a variety of quasi-phase-matching (QPM) effects, such as the collective envelope effect associated with multiple QPM resonances, the enhanced second- harmonic generation due to multiple reciprocal vectors etc., are suggested theoretically and verified experimentally. By rotating the nonlinear photonic crystal sample, the dynamic evolution of these QPM effects has also been observed, which agreed well with the Ewald shell model.

Detection of defects on the surface of a semiconductor by terahertz surface plasmon polaritons.

We propose a new method for detecting small defects on the surface of a semiconductor by analyzing the transmission spectrum of terahertz surface plasmon polaritons. The field distributions caused by the detection of defects of different sizes are simulated. Experimentally, using a terahertz time domain spectrometer, we measure the transmission spectrum of terahertz surface plasmon polaritons passing through particles on the surface of an intrinsic InSb wafer. Our results show that the measured temporal waveform and frequency spectra are distinctly changed due to the presence of the particles, thereby confirming the effectiveness of this method for detecting defects. For increased detection efficiency, the frequency of the surface plasmon polaritons has to be slightly lower than the plasma frequency of the semiconductor. In comparison with traditional methods, our approach offers the merits of detecting both on-surface and subsurface defects, which is critical in monitoring the quality of semiconductor wafers.

Rigorous intensity and phase-shift manipulation in optical frequency conversion.

A simple method is employed to investigate the nonlinear frequency conversion in optical superlattices (OSL) with pump depletion. Four rigorous phase-matching conditions for different purposes are obtained directly from the nonlinear coupled equations, and the resulting OSL domain structures are generally aperiodic rather than periodic. With this method, not only the intensity but also the phase-shift of the harmonic waves can be manipulated at will. The second-harmonic generation of Gaussian beam is further investigated. This work may provide a guidance for the practical applications of designing nonlinear optical devices with high conversion efficiency.

Miniature spectrometer based on diffraction in a dispersive hole array.

We present an ultra-compact spectrometer that uses a 10×10 hole array as the dispersive component. Our analysis shows that the two-dimensional intensity distribution can be modeled by a system of simultaneous linear equations when the size of each hole in the dispersive component has been pre-designed appropriately. One can readily recover the spectral contents of the input radiation by solving the linear equation system with regularized procedure. Experimental results show that the reconstruction range is at least within the entire visible band, which can be further extended if a near-infrared CCD is used. One therefore envisions strong potential for many wavelength analysis applications.

Nonlinear optical Fourier transform in an optical superlattice with "x+2" structure.

We proposed a simple method to realize optical Fourier transform during the nonlinear wave shaping processes. In this method, an integrated optical superlattice is designed to realize multiple optical functions, which plays important roles in both the nonlinear harmonic generation process and the optical Fourier Transform process. We demonstrated our method by the nonlinear generation of Airy beams as an example. It is a universal method for beam shaping and is of practical importance for designing compact nonlinear optical devices.

Asymmetric transmission and optical rotation of a quasi-3D asymmetric metallic structure.

Three-dimensional (3D) asymmetric plasmonic structures possessing asymmetric optical transmission properties have been widely studied. However, these structures have limitations for application due to fabrication techniques. Here, a quasi-3D asymmetric structure built up by a metallic rod-shaped particles layer and a metallic L-shaped holes layer was fabricated by the sputtering and the focused ion beam (FIB) milling. A broadband (1000-1600 nm) asymmetric transmission and optical rotation have been demonstrated experimentally. Numerical calculations show that the coupling between the cavity and particle plasmonic resonances contributes to this effect.

Nonlinear volume holography for wave-front engineering.

The concept of volume holography is applied to the design of an optical superlattice for the nonlinear harmonic generation. The generated harmonic wave can be considered as a holographic image caused by the incident fundamental wave. Compared with the conventional quasi-phase-matching method, this new method has significant advantages when applied to complicated nonlinear processes such as the nonlinear generation of special beams. As an example, we experimentally realized a second-harmonic Airy beam, and the results are found to agree well with numerical simulations.

Amplified spontaneous emission via the coupling between Fabry-Perot cavity and surface plasmon polariton modes.

We demonstrated amplified spontaneous emission by embedding dye molecules within a dielectric layer of a metal-dielectric-metal subwavelength structure. It was reinforced when a strong coupling occurred between the Fabry-Perot mode supported by the dielectric layer and the surface plasmon polariton mode supported by the adjacent metallic grating. Here, we adjust the two mode interaction via tuning the depth of the metallic grating grooves. The stronger the interaction, the smaller the full width at half-maximum of the emission spectra and the lower the threshold of the amplified spontaneous emission.