This paper proposes a method for characterizing the junction temperature of light-emitting diodes (LEDs) by using two parameters, and the selected reference method is used to eliminate the self-heating effect of white LEDs. The constant current source is used to drive, which improves the practicability and reduces the measurement cost. The junction temperature of cold and warm white LED is measured with a small current of 50–400 mA as the driving current. The studied ambient temperature range is 30–80 °C. The results show that the relationship between the spectrum valley value of the calibration function, the full width at half maximum (FWHM), driving current, and junction temperature can be combined with a high degree of the fitting. Compared with the measurement results of the forward voltage method, the maximum error of the measurement of the two-parameter joint characterization junction temperature method is only 2.38 °C. It is a low-cost, practical, and effective junction temperature measurement method for white LEDs.

The static levelling system has significant value in the settling measurement of the structures. A novel pressurized static level based on circular structure is designed by using fiber Bragg grating (FBG) sensing technology in this research. The variation of the level pressure in the connecting vessel can be transmitted through the diaphragm to the FBG of the circular ring. The Ritz method is used to calculate the lateral deformation of the circular ring under the concentrated force, constructing the theoretical sensitivity model of the sensor. Further, finite element simulation and static experiments are applied to modify and verify it. According to the experimental data, two FBGs arranged horizontally along the circular ring, multiplying the sensitivity of the FBG static level to about 4.75 pm/mm, while the resolution can reach 0.02 mm. In addition, the temperature compensation of the sensor can be realized by the synergistic change of the measurement point and the reference point within the system of connecting vessel.

Top-emitting organic light-emitting diodes (TEOLEDs) have attracted extensive attention for their high brightness and flat-panel display. However, the efficiency roll-off at high brightness is the issue that needs to be resolved for further practical applications using TEOLED devices. Herein, a serial of high-efficiency tandem TEOLED introducing a fullerene/zinc-phthalocyanine organic semiconductor heterojunction as a charge generation layer is demonstrated. With unique photovoltaic properties, the charge generation layer can absorb part of the photons emitted by the emission layer (Ir(ppy)₃) and generate electrons and holes. By optimizing the thickness of the charge generation layer, the pure green electroluminescent TEOLED device manufactured has a high brightness of 156 000 cd/cm² and a maximum current efficiency of 86 cd/A. Importantly, relying on the energy between the photovoltaic and the microcavity effects, only 1.5% of the efficiency roll-off is obtained at 1 000–10 000 cd/cm². Introducing fullerene/zinc-phthalocyanine as the charge-generating layer provides a promising alternative for developing high-efficiency tandem TEOLED devices.

The generation of periodic triangular waveform with variable symmetrical coefficient based on a dual-parallel Mach-Zehnder modulator (DP-MZM) is demonstrated in this work. By properly setting the modulation index and bias points of DP-MZM, desired symmetric/asymmetric triangular waveforms can be generated. Then applying the generated triangular waveform into an amplitude modulator (AM), a single-period signal can be extracted to explore the optical wavelength conversion induced by the self-phase modulation (SPM) effect in a high nonlinear fiber (HNLF). Wavelength shifts of triangular waveforms with different coefficients (10%, 20%, 30%, 40% and 50%) are calculated. In addition, the influence of key parameters of HNLF on the wavelength conversion is analyzed in detail.

A theoretical model concerning active Q-switching of an Fe: ZnSe laser pumped by a continuous-wave (CW) 2.8 µm fiber laser is developed. Calculations are compared with the recently reported experiment results, and good agreement is achieved. Effects of principal parameters, including pump power, output reflectivity, ion concentration and temperature of crystal, on the laser output performance are investigated and analyzed. Numerical results demonstrate that similar to highly efficient CW Fe: ZnSe laser, low temperature of the crystal is significant to obtain high peak power Q-switched pulses. The numerical simulation results are useful for optimizing the design of actively Q-switched Fe: ZnSe laser.