Impact of the spatial coherence on self-interference digital holography

Owing to the unique feature that the signal and reference waves of self-interference digital holography (SIDH) contain the same spatial information from the same point of object, compared with conventional digital holography, the SIDH has the special spatial coherence properties. We present a statistical optics approach to analyzing the formation of cross-correlation image in SIDH. Our study reveals that the spatial coherence of illumination light can greatly influence the imaging characteristics of SIDH, and the impact extent of the spatial coherence depends substantially on the recording distance of hologram. The theoretical conclusions are supported well by numerical simulation and optical experiments.     

同轴相移数字全息中相移角的选取及相移误差的消除

基于两步同轴相移数字全息,首先从理论上分析了记录时不同相移角的选取及相移误差对再现像的影响,并给出了一种利用再现像所有抽样点的强度偏差之和作为评价标准,通过逐步改变理论设定相移角值来寻找实际相移角的相移误差消除新方法;其次对二步相移数字全息中记录时参考光波最佳相移角的选取作了计算机模拟,发现只有将参考光波的相移角选择在一定范围内,再现像的噪声较小;最后利用计算机模拟了相移误差消除,验证了所提方法的可行性.     

Electromagnetic transmission in configurations composed of two one-dimensional perfect electric conductor metal gratings

We study transmission properties in configurations composed of two single metal gratings with different thicknesses. Choosing the perfect electric conductor excludes the influence of intrinsic material dispersion on transmission behaviors; and as such, we aim to reveal the contribution of geometric dispersion to electromagnetic transmission. Transmission suppression line, instead of a transmission suppression point, is discovered, denoting the curve of the wavelength versus the interval or the lateral displacement between the two single gratings when the transmission suppression appears. A simplified model is proposed to comprehend the underlying physics of this special phenomenon.     

Q-switched mode-locked diode-pumped Nd:YVO4 laser with a saturable Bragg reflector

We demonstrated a diode-pumped passively Q-switched mode-locked Nd:YVO4 laser by using a relaxed saturable Bragg reflector (SBR). Stable mode-locked pulse train with the repetition rate of ～230 MHz was achieved and the pulse train was modulated by the Q-switched envelope with the repetition rate of ～150 kHz. The maximum output of 4 W was obtained under the pump power of 13.5 W. The optical-to-optical efficiency was 30%. We also discussed the transition of each process having emerged.     

Ab Initio Study of Structural and Electronic Properties of Hexagonal BC2N

We investigate hexagonal BC2N in graphite unit cells using the first-principles method and calculate the total energies, lattice parameters, and electronic band structures after full relaxation. It is shown that stable hexagonal BC2N should be stacked sequentially with one graphite layer and one h-BN layer. The density of states indicates that this structure should have metallicity.     

Ultrabroadband SCG with quasi-continuous wave nanosecond-long pump pulses in PCF

An ultrabroadband supercontinuum (SC) is demonstrated in a pure silica photonic crystal fiber (PCF) pumped by quasi-continuous wave nanosecond-long pulses at 1,064 nm. The generated SC spectra extending from 450 to at least 2,400 nm have the salient feature of a short wavelength regime below the pump wavelength, which is much higher in intensity than the long-wavelength over the pump wavelength. The influence of pump power and repetition rates on SC generation (SCG) is explored. Results suggest that this pump source has both the advantages of short-pulse and continuous-wave pumps for SCG.     

Partially Diffusive Helium-Silica Compound under High Pressure

Helium is the second most abundant element in the universe, and together with silica, they are important components of giant planets. Exploring the reactivity and state of helium and silica under high pressure is crucial for understanding of the evolution and internal structure of giant planets. Here, using first-principles calculations and crystal structure predictions, we identify four stable phases of a helium-silica compound with seven/eight-coordinated silicon atoms at pressure of 600–4000 ...     

含金属散射体的中红外无序介质的光子定域化理论研究

基于Mie散射理论发现,各种金属在中红外区的各个频率点上的散射行为均极为相近,是一种在中红外区反照率高但散射效率较低的散射体.在浓度为10%时,介质的定域化参量最小只能达到6.6,并且与体系的常用基质材料无关.数值研究揭示了这种金属散射体系统与低吸收、高折射率散射体系统间的内在联系 关键词： 光子定域化 无序介质 中红外 Mie散射 金属     

Multi-Path Ghost Imaging by Means of an Additional Time Correlation

Ghost imaging functions achieved by means of the spatial correlations between two photons is a new modality in imaging systems. With a small number of photons, ghost imaging is usually realized based on the position correlation of photon pairs produced from the spontaneous parametric down-conversion process. Here we demonstrate a way to realize multi-path ghost imaging by introducing an additional time correlation. Different delays of paths will induce the shift of the coincidence peak, which carries the information about objects. By choosing the suitable coincidence window, we obtain images of three objects simultaneously, with a visibility of 87.2%.This method provides insights and techniques into multi-parameter ghost imaging. It can be applied to other correlated imaging systems, for example, quantum spiral imaging.     

贯通大中学物理综合能力培养的物理学术竞赛教学模式

本文介绍基于国际青年物理学家锦标赛的物理教学实践和物理学术竞赛在国内的中学和大学的开展情况,该活动不仅推动了物理教学在方法、内容和考核等方面的改革,并推动开设了系列化开放互动课程,关注学生综合能力的培养,有效地促进了中学和大学物理教育的有机衔接,是一种培养综合性物理创新人才的有益的创新尝试.