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Absorptive reduction and width narrowing in Λ-type atoms confined between two dielectric walls 下载免费PDF全文
This paper investigates the absorptive reduction and the width narrowing of electromagnetically induced transparency (EIT) in a thin vapour film of A-type atoms confined between two dielectric walls whose thickness is comparable with the wavelength of the probe field. The absorptive lines of the weak probe field exhibit strong reductions and very narrow EIT dips, which mainly results from the velocity slow-down effects and transient behaviour of atoms in a confined system. It is also shown that the lines are modified by the strength of the coupling field and the ratio of L/λ, with L the film thickness and λthe wavelength of the probe field. A simple robust recipe for EIT in a thin medium is achievable in experiment. 相似文献
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Numerical study of converting beat-note signals of dual-frequency lasers to optical frequency combs by optical injection locking of semiconductor lasers 下载免费PDF全文
Chenhao Liu 《中国物理 B》2022,31(8):84205-084205
The optical injection locking of semiconductor lasers to dual-frequency lasers is studied by numerical simulations. The beat-note signals can be effectively transformed to optical frequency combs due to the effective four wave-mixing in the active semiconductor gain medium. The low-noise Gaussian-like pulse can be obtained by locking the relaxation oscillation and compensating the gain asymmetry. The simulations suggest that pulse trains of width below 30 ps and repetition rate in GHz frequency can be generated simply by the optical injection locking of semiconductor lasers. Since the optical injection locking can broaden the spectrum and amplify the optical power simultaneously, it can be a good initial stage for generating optical frequency combs from dual-frequency lasers by multi-stage of spectral broadening in nonlinear waveguides. 相似文献
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Photoluminescence of multiwalled carbon nanotubes excited at different wavelengths 总被引:1,自引:0,他引:1 下载免费PDF全文
In this paper the multiwalled carbon nanotubes (MWNTs) were synthesized by a
chemical vapour deposition and the SEM graph shows that the sample has good
construction. The micro-Raman spectrum shows the characteristic line of the MWNTs
and an additional line produced by the defects on the outer surface of MWNTs. The
photoluminescence (PL) spectra observed experimentally are variable under different
excitation wavelengths and the strong excitation wavelength dependence of
luminescence indicates a distribution of emitters which include electron $\pi$ in
excited states and the Van Hove singularities. The absorption spectra confirm the
transition channels which are consistent with the PL emission. 相似文献
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使用正硅酸乙酯、硼酸和硝酸铝为前驱体,硝酸铕为掺杂剂,以溶胶-凝胶法制备了Eu单掺和Eu、B共掺的SiO2干凝胶,并成功地在钠钙玻璃上制备了光洁度很好的掺杂SiO2多层薄膜.利用荧光光谱、红外光谱(IR)、X射线衍射(XRD)等技术研究了B离子、退火温度对样品发光性能的影响.荧光光谱显示发光体能产生很强的红色发光,经500℃以上退火处理,产生6条谱带,分别归属于Eu3+的5D0→7FJ(J=0, 1, 2, 3, 4)的电子跃迁, 5D0→7F1的跃迁分裂为两个峰.实验结果表明,B离子的加入,由于在材料中形成了Si-O-B键,使Eu3+的配位环境的对称性降低,加强了Eu3+的红光发射.退火处理改变了材料的网络结构,降低了水和羟基的含量有助于提高发光强度,但退火温度太高(850℃),发生了荧光猝灭效应,源于稀土离子发生位置迁移形成的团簇.XRD测试结果显示材料是非晶态的. 相似文献
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