耦合光学微腔的频率调谐过程分析

不同的频率失谐会在耦合光学微腔激发出不同的工作模式.以两个耦合光场的非线性薛定谔方程为理论模型,分别研究了失谐参量正调谐和负调谐过程中微腔内光场的变化.理论分析结果表明,在正失谐区域中,腔内光场可由多脉冲形式演变为亮孤子,但亮孤子存在范围较小,当失谐参量过大时,腔内光场会演化为直流分布.在负失谐区域,腔内可以形成较高功率"图灵环"形式的光场.当耦合微腔没有发生频率失谐,或者失谐参量接近0时,腔内只能形成混沌形式的光场分布.当耦合微腔内激发出光孤子后,通过选取合适的失谐参量和抽运功率,可在腔内维持稳定的亮孤子.此外还可通过继续调谐第一个微腔的失谐参量,将亮孤子转变为低功率的"图灵环".理论分析结果对耦合微腔的实验研究具有重要意义.     

Analysis of dark soliton generation in the microcavity with mode-interaction

Mode-interaction plays an important role in the dark soliton generation in the microcavity. It is beneficial to the excitation of dark solitons, but also facilitates a variety of dark soliton states. Based on the non-normalized Lugiato-Lefever equation, the evolution of dark soliton in the microcavity with mode-interaction is investigated. By means of mode-interaction, the initial continuous wave(CW) field evolves into a dark soliton gradually, and the spectrum expands from a single mode to a broadband comb. After changing the mode-interaction parameters, the original modes which result in dual circular dark solitons inside the microcavity, are separated from the resonant mode by 2 free spectral ranges(FSR). When the initial field is another feasible pattern of weak white Gaussian noise, the large frequency detuning leads to the amplification of the optical power in the microcavity, and the mode-interaction becomes stronger. Then, multiple dark solitons, which correspond to the spectra with multi-FSR, can be excited by selecting appropriate mode-interaction parameters. In addition, by turning the mode-interaction parameters, the dark soliton number can be regulated, and the comb tooth interval in the spectrum also changes accordingly. Theoretical analysis results are significant for studying the dark soliton in the microcavity with mode-interaction.     

First principles investigation on Li or Sn codoped hexagonal tungsten bronzes as the near-infrared shielding material

The 52% energy of the solar radiation is contributed by near-infrared radiation (NIR, 780-2500 nm). Therefore, the material design for the energy-saving smart window, which can effectively shield NIR and has acceptable visible transmittance, is vital to save the energy consumed on the temperature control system. It is important to find a non-toxic stable material with excellent NIR-shielding ability and acceptable visible transmittance. The systematic first-principles study on Li_xSn_yWO₃ (x=0, 0.33, 0.66, and y=0, 0.33) exhibits that the chemical stability is a positive correlation with the doping concentration. After doping, the Fermi-energy upshifts into the conduction band, and the material shows metal-like characteristics. Therefore, these structures Li_xSn_yWO₃ (except the structure with x=0.33 and y=0) show pronounced improvement of NIR shielding ability. Our results indicate that when x=0 and y=0.33, the material exhibits the strongest NIR-shielding ability, satisfying chemical stability, wide NIR-shielding range (780-2500 nm), and acceptable visible transmittance. This work provides a good choice for experimental study on NIR shielding material for the energy-saving window.