Design and characterization of guided mode resonance filters with the improved structure for facile fabrication

In this study, a guided mode resonance filter with the improved structure for facile fabrication is designed; the properties of the designed filters are simulated by rigorous coupled wave analysis. It is found that the resonance wavelength and spectral linewidth are slightly increased with the increasing of the grating thickness, and seldom changed with the thickness of the grating filling factor, as the parameter error of the grating thickness and the grating filling factor are deviated from the designed value by ±10%, respectively, which are very favorable for simplifying preparation process of the GMR filter.     

Laser frequency stabilization based on Sagnac interferometric spectroscopy

A simple method based on Sagnac interferometric spectroscopy (SIS) is applied for frequency stabilization of diode lasers. Sagnac interferometric spectra of rubidium vapor are investigated both theoretically and experimentally. The interference signal at the output of the Sagnac interferometer displays a sharp dispersion feature near the atomic resonance. This dispersion curve is used as the feedback error signal to stabilize the laser frequency. Linewidth of a diode laser is stabilized down to 1 MHz by this modulation-free method.     

Random laser action in bovine semen

Experiments using bovine semen reveal that the addition of a high-gain water soluble dye results in random laser action when excited by a Q-switched, frequency doubled, Nd:Yag laser. The data shows that the linewidth collapse of the emission is correlated to the sperm count of the individual samples, potentially making this a rapid, low sample volume approach to count determination.     

Enhanced locking region in injection-locked two-section lasers

In this Letter, we investigate the criteria for achieving an enhanced stable locking region in the parameter space of injected field E_inj and frequency detuning ω in two-section semiconductor lasers subject to optical injection. Using the rate equations, a stability analysis is performed and the conditions for an enhanced locking region are deduced from the requirement for the average linewidth enhancement factor appearing in the locking-bandwidth equation to be close to zero. We calculate a stability map for an injection-locked two-section laser with an almost-symmetrical locking region that is greatly enhanced compared to a single-section injection-locked laser with identical material and control parameters.     

辐射交联顺1,4-聚丁二烯的NMR研究

用１３Ｃ ＮＭＲ方法,测定了辐射交联顺１,４ 聚丁二烯在室温下的自旋 晶格弛豫时间（Ｔ１）,核Ｏｖｅｒｈａｕｓｅｒ因子（ＮＯＥ）,和１３Ｃ ＮＭＲ线宽．以及凝胶本体１Ｈ ＮＭＲ的Ｔ１和Ｔ２弛豫时间,结果表明,辐射交联顺１,４ 聚丁二烯体系中,随着凝胶含量的增加各碳核质子的Ｔ１值变化很小,而—ＣＨ２—核的ＮＯＥ因子明显降低和１３Ｃ ＮＭＲ线宽增宽．以及１Ｈ ＮＭＲ的Ｔ１和Ｔ２表现的双指数弛豫特性反映了交联体系中大分子链段长程运动受阻以及饱和交联叔碳核—ＣＨ对链段运动的影响．     

线宽误差对菲涅耳透镜衍射效率的影响

基于标量衍射理论,首先得出存在线宽误差情况下4阶菲涅耳透镜衍射效率的解析式;并以 4阶、8阶和16阶菲涅耳透镜为例,进行计算机模拟计算并系统分析线宽误差对菲涅耳透镜衍射效率的影响。通过实验测量16阶菲涅耳透镜的线宽误差,分析其对16阶菲涅耳透镜衍射效率的影响。模拟计算结果对多阶菲涅耳透镜的制作提供重要的理论指导。     

Line shape and lifetime in argon 2p electron spectroscopy

The argon 2p photoelectron spectrum and the argon L₃M₂₃M₂₃ ¹S₀ Auger spectrum have been measured at several photon energies between 6 and 80 eV above the 2p_3/2 threshold with an instrumental line width significantly smaller then the natural line width. The spectra are described well by the theory of van der Straten et al. [Z. Phys. D 8 (1988) 35] provided that allowance is made for the instrumental resolution and measurements are made at a sufficiently low pressure. The lifetime (Lorentzian) line width determined from these measurements for the core-ionized atom is 112±3 meV, in good agreement with the line width for the 2p_3/2→4s core-excited state, 114±2 meV, indicating that the 4s electron has little influence on the Auger decay rate. Remeasurement of the line width for the carbon 1s hole in carbon dioxide gives values in good agreement with the previous measurement of 99 meV.     

Chemical Approach Towards Broadband Spintronics on Nanoscale Pyrene Films

The injection of pure spin current into the non-magnetic layer plays a crucial role in transmitting, processing, and storing data information in the realm of spintronics. To understand broadband molecular spintronics, pyrene oligomer film (≈20 nm thickness) was prepared using an electrochemical method forming indium tin oxide (ITO) electrode/pyrene covalent interfaces. Permalloy (Ni₈₀Fe₂₀) films with different nanoscale thicknesses were used as top contact over ITO/pyrene layers to estimate the spin pumping efficiency across the interfaces using broadband ferromagnetic resonance spectra. The spintronic devices are composed of permalloy/pyrene/ITO orthogonal configuration, showing remarkable spin pumping from permalloy to pyrene film. The large spin pumping is evident from the linewidth broadening of 5.4 mT at 9 GHz, which is direct proof of spin angular momentum transfer across the interface. A striking observation is made with the high spin-mixing conductance of ≈1.02×10¹⁸ m⁻², a value comparable to the conventional heavy metals. Large spin angular moment transfer was observed at the permalloy-pyrene interfaces, especially at the lower thickness of permalloy, indicating a strong spinterface effect. Pure spin current injection from ferromagnetic into electrochemically grown pyrene films ensures efficient broadband spin transport, which opens a new area in molecular broadband spintronics.     

Contribution of polaron hopping to the electron paramagnetic resonance linewidth in La1−xCaxMnO3 and related materials

We analyze the contribution of polaron hopping to the electron paramagnetic resonance linewidth in La_1−xCa_xMnO₃ and related materials. The material is assumed to be in the paramagnetic phase and the conductivity is associated with the activated polaron hopping. It is also assumed that the adiabatic, small polaron picture is appropriate so that the conductivity varies as exp[−E_a/T]/T, where E_a denotes the polaron activation energy. The polaron contribution to the linewidth is given by the expression C[χ₀(T)/χ(T)]exp[−E_a/T] where χ₀(T) is the Curie susceptibility (∼1/T), χ(T) is the measured susceptibility and C is a material-dependent parameter. Various experimental studies reporting polaron contributions to the linewidth are discussed. It is pointed out that fitting the linewidth to the functional form ΔH₀+(A/T)exp[−E_a/T] is not physically justified. In the high temperature–mean field regime, the exchange narrowed width, (1−Θ/T)k(∞), where Θ is the paramagnetic Curie temperature, replicates the exponential functional form with reasonable values for the activation energy. From previous measurements of the conductivity that showed activated polaron hopping as the leading transport mechanism, we concluded that the linewidth in La_0.7Ca_0.3MnO₃ is a sum of exchange narrowing and one-phonon spin–lattice terms with no evidence of a contribution from polaron hopping or band transport as had been previously proposed. A similar conclusion is reached for La_0.8Ca_0.2MnO₃, nanometer-sized La_0.9Ca_0.1MnO₃, and La_0.9Te_0.1MnO₃.     

利用原子的塞曼光谱对半导体激光器进行稳频

中性原子的超精细能级在磁场中产生塞曼分裂 ,另外 ,左旋和右旋圆偏振光激发下原子的跃迁选择定则不同 ,因此 ,原子在超精细塞曼能级间的吸收谱峰相对无磁场条件下的吸收谱峰有一定的移动。利用这一点 ,验证了一种简单、灵活的方法对半导体激光器进行稳频 ,使激光器的线宽稳到小于 1MHz。通过对实验结果的分析 ,发现由左旋和右旋圆偏振光激发引起的原子吸收谱峰移动之和与饱和吸收峰半高宽相等时 ,稳频效果最好