Thickness dependent magnetic and ferroelectric properties of LaNiO3 buffered BiFeO3 thin films

BiFeO₃ (BFO) thin films with thickness increasing from 40 to 480 nm were successfully grown on LaNiO₃ (LNO) buffered Pt/Ti/SiO₂/Si(100) substrate and the effects of thickness evolution on magnetic and ferroelectric properties are investigated. The LNO buffer layer promotes the growth and crystallization of BFO thin films. Highly (100) orientation is induced for all BFO films regardless of the film thickness together with the dense microstructure. All BFO films exhibited weak ferromagnetic response at room temperature and saturation magnetization is found to decrease with increase in film thickness. Well saturated ferroelectric hysteresis loops were obtained for thicker films; however, the leakage current dominated the ferroelectric properties in thinner films. The leakage current density decreased by three orders of magnitude for 335 nm film compared to 40 nm film, giving rise to enhanced ferroelectric properties for thicker films. The mechanisms for the evolution of ferromagnetic and ferroelectric characteristics are discussed.     

简易超声波换能器频率测试仪的研究

对超声波换能器频率测试系统进行了探讨，并在此基础上提出了改装设想，分析了所研究的简易超声波换能器频率测试仪的电路原理及实验结果。     

Submillimeter-wave heterodyne spectroscopy with a compact solid state radiometer

A compact, solid state submillimeter-wave heterodyne radiometer has been developed and was used to measure spectral characteristics of a water vapor jet in a space simulation chamber. Features of the 557 GHz water vapor line profile were observed in significantly greater detail than in previous experiments through an increased sensitivity and improved frequency resolution (600 kHz). The local oscillator of the radiometer consisted of a frequency multiplication chain which was driven by an InP Gunn oscillator at 92.6 GHz, and which contained a frequency tripler and harmonic mixer in cascade. The front end of the receiver had a noise temperature of 4500 K (DSB) at 555 GHz, consumed 3 W and weighed 3 kg. This advance in technology is particularly relevant to submillimeter-wave radiometry from a space-based platform.     

两能级原子在激光衰波场中的共振反射

在共振情况下求解两能级原子在激光衰波场中的薛定谔方程，得到了基态原子反射率Ｒｇ、激发态原子反射率Ｒｅ以及原子总反射率Ｒｔ的解析表达式。然后通过数值计算，详细讨论了Ｒｇ、Ｒｅ，Ｒｔ与拉比频率，原子垂直于靶面方向运动的动能的依赖关系，得到一些有意义的结果。     

Enabling arbitrary wavelength frequency combs on chip

A necessary condition for generation of bright soliton Kerr frequency combs in microresonators is to achieve anomalous group velocity dispersion (GVD) for the resonator modes. This condition is hard to implement in the visible as well as ultraviolet since the majority of optical materials are characterized with large normal GVD in these wavelength regions. We overcome this challenge by borrowing ideas from strongly dispersive coupled systems in solid state physics and optics. We show that photonic compound ring resonators can possess large anomalous GVD at any desirable wavelength, even if each individual resonator is characterized with normal GVD. Based on this concept, we design a mode‐locked frequency comb with thin‐film silicon nitride compound ring resonators in the vicinity of the rubidium D₁ line (794.6 nm) and propose to use this optical comb as a flywheel for chip‐scale optical clocks.

     

Theoretical and Experimental Studies on a Metallorganic Complex of (Isopropylxanthato)(Phenyl)Mercury(I) [Hg(I)(C<Subscript>6</Subscript>H<Subscript>5</Subscript>)(C<Subscript>4</Subscript>H<Subscript>7</Subscript>OS<Subscript>2</Subscript>)]

The title compound, (isopropylxanthato)(phenyl)mercury(I), was synthesized and characterized by elemental analysis, IR and thermogravimetric analysis. Density functional theory (DFT) method calculations were performed at B3LYP/CEP-121G and B3LYP/CEP-31G levels of theory, respectively. Vibrational frequencies were predicted, assigned, compared with the experimental values, and they are supported each other. The calculated results show that the strength of bond Hg—C is stronger than that of Hg—S, which is good agreement with the experimental data. The calculations of the second order optical nonlinearity and electronic absorption spectra are also performed.     

Timing characteristics of the scintillation response of Gd3Al2Ga3O12:Ce and Gd3Al2.6Ga2.4O12:Ce single crystal scintillators

The timing characteristics of scintillation response of Czochralski-grown Gd₃Al₂Ga₃O₁₂:Ce and Gd₃Al_2.6Ga_2.4O₁₂:Ce single crystals were compared. The photoelectron yield, scintillation decay times, and coincidence time resolution were measured. At 662 keV γ-rays, the photoelectron yield of 6200 phe MeV⁻¹ obtained for Gd₃Al₂Ga₃O₁₂:Ce is higher than that of 4970 phe MeV⁻¹ obtained for Gd₃Al_2.6Ga_2.4O₁₂:Ce, while an inferior energy resolution of the former (7.2% vs. 5.6%) is observed. Scintillation decays are approximated by sum of exponentials with the dominant fast component decay time and its relative intensity of 89 ns (73%) for Gd₃Al₂Ga₃O₁₂:Ce and 136 ns (69%) for Gd₃Al_2.6Ga_2.4O₁₂:Ce. The coincidence time resolution obtained for Gd₃Al₂Ga₃O₁₂:Ce is superior than that of Gd₃Al_2.6Ga_2.4O₁₂:Ce. The normalized time resolution was also discussed in terms of a number of photoelectrons and decay characteristics of the light pulse.     

High Power THz Undulator Radiation from Linear Accelerator

A 30-MeV femto-second electron linac is built at the Shanghai Institute of Applied Physics, which can produce high power, coherent THz undulator radiation. We report the experimental facility and measurement of the power, frequency spectrum. First experiments show the averaged power at THz to be about 20mW.     

Recent highlights in graphite furnace atomic absorption spectrometry

Graphite furnace atomic absorption spectrometry (GFAAS) is an elemental analysis technique that has been employed for virtually all types of samples. Traditionally, hollow cathode lamps, line excitation sources, have been employed for excitation. However, in the past two decades, high resolution continuum source (HR CS) GFAAS has been shown to offer greater potential for multielemental analysis, greater flexibility in wavelength selection, the ability to determine molecules, and better characterization and correction for spectral backgrounds. The recent analytical literature is critically reviewed, including solubilization and preconcentration procedures. Solid and slurry sampling have been the focus of recent work; in particular, the enhanced capabilities of HR CS GFAAS provide green methodology with suitable sensitivity, precision, and accuracy. GFAAS has also been employed for elemental speciation, including characterization of forms using the atomization profiles.     

Instantaneous frequency measurement based on complementary microwave photonic filters with a shared Mach-Zehnder interferometer

A novel configuration using only one Mach-Zehnder interferometer (MZI) for photonic-assisted instantaneous microwave frequency measurement is proposed. The amplitude comparison function (ACF), related to the input microwave frequency while independent of the input optical power and modulate index, is achieved by using a ratio of low-pass to bandpass frequency responses introduced by intensity and phase modulation with a shared MZI. The microwave frequency can be estimated by the measured ACF. A proof-of-concept experiment for measurement of RF from 5 to 10 GHz is successfully demonstrated with the measurement errors less than ± 0.2 GHz.