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High-<i>Q</i> lithium niobate (LN) optical micro-resonators are excellent platform for future applications in optical communications, nonlinear optics and quantum optics. To date, high <i>Q</i> factors are typically achieved in LN using either dielectric masks or femtosecond laser ablation, while the more standard and commonly available lift-off metallic masks are often believed to lead to rough sidewalls and lowered <i>Q</i> factors. Here we show that LN microring resonators with strong light confinement and intrinsic <i>Q</i> factors over 1 million can be fabricated using optimized lift-off metallic masks and dry etching processes, corresponding to a waveguide propagation loss of ~ 0.3 dB/cm. The entire process is fully compatible with wafer-scale production and could be transferred to other photonic materials.
Chinese Optics Letters
The photoelectric properties of In<sub>0.3</sub>Ga<sub>0.7</sub>As solar cell applied in laser wireless power transmission(LWPT) was studied when irradiated by 1070nm continuous(CW) laser of various intensities. The influences of laser intensity on solar cell parameters extracted by pollination algorithm were analyzed quantitatively. Results show that conversion efficiency of the cell rose to the maximum and then decreased rapidly in the laser intensity range of 50-900mW/cm<sup>2</sup>. With higher energy laser irradiation, the rise of ideality factor and reverse saturation current would lead to the degradation of voltage at maximum power point, which was the main reason for the decrease of conversion efficiency. The results provide basis for choosing the appropriate input energy in the case of different transmission systems.
Chinese Optics Letters
The impact pendulum and torsion pendulum are mostly applied in impulse coupling experiments of high energy laser irradiation on space debris. It is difficult to achieve multi-pulse experiment and thus hard to analyze the multi-pulse impulse coupling effect. Here, we designed a new recoil impulse experimental measurement system of non-contact, multi-degree of freedom and multi-pulse irradiation is designed. The system used a low-pressure and low-temperature vacuum chamber to simulate the space environment, the pinning effect of magnetic levitation to achieve aluminum target suspension and high-speed cameras to record the displacement over time to calculate the impulse of target. Then the impulse coupling experiment of multi-pulse laser irradiation on aluminum target was performed. The result shows that the multi-pulse impulse coupling effect is not the linear accumulation of coupling results by every single pulse and mul-ti-pulse coefficient decreases with the increase of the number of pulses, and eventually stabilizes as the decrease getting smaller and smaller.
Chinese Optics Letters
Quaternary chalcogenide Cu2FeSnS4(CFTS) nanoparticles, as a kind of potential absorber layer material in thin film solar cells (TFSCs), were successfully synthesized by using a convenient solvothermal method. Alkali element K is incorporated into CFTS thin films in order to further improve the surface morphology and the optical properties of related films. X-ray diffraction (XRD), Raman spectroscopy and field emission scanning electron microscopy (FESEM) were used to characterize the phase purity, morphology and composition of CFTS particles and thin films. The results show that the particle elemental ratios of Cu/(Fe+Sn) and Fe/Sn are 1.2 and 0.9, respectively, which are close to the characteristics of stoichiometric CFTS. The band gaps of CFTS films before and after doping K ions are estimated to be 1.44 eV and 1.4 eV with an error of ±0.02 eV.
2017, 13(4): 291
The Ho3+/Pr3+co-doped NaYF4single crystals with various Pr3+concentrations and constant Ho3+molar percentage of ~1% were grown by an improved Bridgman method. Compared with the Ho3+single-doped NaYF4crystal, an obviously enhanced emission band at 2.85 μm is observed under 640 nm excitation. The Judd-Ofelt strength parameters (Ω2, Ω4and Ω6) are calculated, the radiative transition probabilities (A), the fluorescence branching ratios (β) and the radiative lifetime (τrad) are obtained in the meantime. The energy transfer from Pr3+to Ho3+and the optimum fluorescence emission of Ho3+ions around 2.85 μm are investigated. Moreover, the maximum emission cross section of above samples at 2.85 μm is calculated to be 0.72×10-20cm2for the NaYF4single crystal with Ho3+molar percentage of 1% and Pr3+molar percentage of 0.5% according to the measured absorption spectrum. All results suggest that the Ho3+/Pr3+co-doped NaYF4single crystal may have potential applications in mid-infrared lasers.
2016, 12(1): 56