Using data from the Longitudinal Study of American Youth (LSAY), we aimed to determine the causal ordering between mathematics anxiety and mathematics achievement. Results of structural equation modelling showed that, across the entire junior and senior high school, prior low mathematics achievement significantly related to later high mathematics anxiety, but prior high mathematics anxiety hardly related to later low mathematics achievement. Mathematics achievement was more reliably stable from year to year than mathematics anxiety. There were statistically significant gender differences in the causal ordering between mathematics anxiety and mathematics achievement. Prior low mathematics achievement significantly related to later high mathematics anxiety for boys across the entire junior and senior high school but for girls at critical transition points only. Mathematics anxiety was more reliably stable from year to year among girls than among boys.

In this paper the stimulated Raman scattering (SRS) effect in high-power fiber amplifiers seeded by the narrow-band filtered superfluorescent source (SFS) is firstly analyzed both theoretically and experimentally. Spectral models for the formation of the SFS and the spectral evolution in high-power fiber amplifiers seeded by filtered SFS are proposed. It is found that the SRS effect in high-power fiber amplifiers depends on the spectral width of the filtered SFS seed. The theoretical predictions are in qualitative agreements with the experimental results.

In this paper, we present our experimental results of a high-power 1018 nm fiber laser and its usage in tandem pump. A record output power of 476 W 1018 nm fiber laser is obtained with an efficiency of 78.2%. Utilizing a specially designed gain fiber, a one-stage high-power monolithic fiber amplifier tandem pumped by six 1018 nm fiber lasers is assembled. A 110 W 1090 nm seed is amplified to 2140 W, and the efficiency is as high as 86.9%. The beam quality factor M2 is measured to be 1.9. Limitations and possible solutions for purchasing higher output power are discussed.

We demonstrate a high-power narrowband all-fiber superfluorescent fiber source employing three-stages master oscillator power-amplifier chain. Narrowband seed light is selected from a broadband-amplified spontaneous-emission source by a spectrum filter combing with fiber circulator and fiber Bragg grating. In the main amplifier, the maximal output power is 1.87 kW with an optical-to-optical conversion efficiency of 77.4% and a full width at half-maximum (FWHM) linewidth of 1.7 nm. The corresponding power fluctuation is ±1.4% in 100 s operation, and no parasitic oscillation or self pulsation is observed. A beam quality of M(2)=1.71 is measured at 1.4 kW output power. This manuscript investigates the spectral evolution in high-power amplification. The central wavelength shifted from 1079.5 nm to 1080.7 nm, and the FWHM linewidth narrowed from 2 nm to 1.7 nm at full power, respectively. These effects could be inferred as hybrid effects of many factors, such as wavelength shifting of pump LD, nonoptimized length of gain fiber, and enhancement of temperature level of gain fiber. The narrowband-maintained characteristic in spectral domain under high-power amplification is significant for applications such as spectral beam combination, and further power scaling is available as the output power is only limited by the pump power.

We present a high power all-fiberized master oscillator power amplifier (MOPA) structured superfluorescent source based on dual-cladding ytterbium-doped fiber. The seed source is a 0.814 W homemade amplified spontaneous emission (ASE) source. Two-stage high power fiber amplifier is utilized to boost the seed power to 1.01 kW with a beam quality of M(x)(2) = 1.688 and M(y)(2) = 1.728. The central wavelength of the output light is 1074.4 nm, and the full width at half maximum (FWHM) linewidth is about 8.1 nm. No self pulsing or relaxation oscillation effect is observed and the power fluctuation is less than 2% in 100 seconds continuous operating. In additional, spectral evolution effects of central-wavelength-drifting and linewidth-narrowing of broadband amplification in high power superfluorescent source system are investigated. To the best of our knowledge, this is the first demonstration of an all-fiberized superfluorescent source with output power exceeding kilowatt.

We demonstrated a ultra-stable pulse based on the high-quality electrochemical delamination exfoliation process black phosphorus.

We present a hundred-watt-level linearly-polarized random fiber laser (RFL) pumped by incoherent broadband amplified spontaneous emission (ASE) source and prospect the power scaling potential theoretically. The RFL employs half-opened cavity structure which is composed by a section of 330 m polarization maintained (PM) passive fiber and two PM high reflectivity fiber Bragg gratings. The 2nd order Stokes light centered at 1178 nm reaches the pump limited maximal power of 100.7 W with a full width at half-maximum linewidth of 2.58 nm and polarization extinction ratio of 23.5 dB. The corresponding ultimate quantum efficiency of pump to 2nd order Stokes light is 86.43%. To the best of our knowledge, this is the first demonstration of linearly-polarized high-order RFL with hundred-watt output power. Furthermore, the theoretical investigation indicates that 300 W-level linearly-polarized single-mode 1st order Stokes light can be obtained from incoherently pumped RFL with 100 m PM passive fiber.

Quantum defect (QD) is an important issue that demands prompt attention in high-power fiber laser. Large QD may aggravate the thermal load in the laser, which would impact the frequency and amplitude noise, mode stability and threaten the security of high-power laser system. Here, we propose and demonstrate a cladding-pumped Raman fiber laser (RFL) with QD <1%. Using the Raman gain of the boson peak in a phosphorusdoped fiber to enable the cladding pump, the QD is reduced to as low as 0.78% with a 23.7 W output power. To our knowledge, this is the lowest QD ever reported in claddingpumped RFL. Furthermore, the output power can be scaled to 47.7 W with a QD of 1.29%. This work not only offers a preliminary platform for the realization of high-power low-QD fiber laser, but also proves low-QD fiber laser's great potential in power scaling.