Study on optical and electrical properties of gold-doped silicon fabricated by femtosecond laser

Microstructured silicon (Si) materials have been fabricated by femtosecond (fs) laser ablation and have been hyperdoped with gold (Au) impurities. The ablated Si materials showed large and thermostable infrared absorption at 1.1–2.5 μm wavelengths, which was contributed by sub-band absorption and laser-induced defects absorption. The Au–Si alloy was formed after laser irradiation onto the Au-coated Si surface, which was determined by XRD characterization. Using N-type Si substrate, the fabricated Au-doped Si performed lower sheet carrier density due to the self-compensation effect between deep donor and acceptor energy lever of Au in bulk Si material. From Hall measurement, both the p- and n- types of Au-doped Si samples can be obtained by controlling the type of Si substrate.     

Terahertz artificial dielectric cuboid lens on substrate for super-resolution images

This paper presents an investigation of terajets formation by dielectric periodic structure at terahertz frequencies (0.1–0.2 THz) in effective medium regime (photonic metamaterial). The dispersions of effective permittivity for periodic structures formed by plastics (ABS, black) were analytically obtained for both regimes. The study of the interaction of a plane wave and artificial cubic dielectric on a substrate parallelepiped to form a subwavelength terahertz beams (terajet) was performed. The results of numerical simulation of S-parameters of structure are discussed. The subwavelength beam waist of terajets about 0.39λ–0.41λ were obtained. The quality factor of terajets are discussed. The results may be applied for creation of methods to obtain subwavelength beams in the terahertz frequency range, and devices based on them. These investigations are opening new research lines such as mesoscale focusing devices for different sensing applications.     

Quantum information-holding single-photon router based on spontaneous emission

In this paper, we propose a single-photon router via the use of a four-level atom system coupled with two one-dimensional coupled-resonator waveguides. A single photon can be directed from one quantum channel into another by atomic spontaneous emission. The coherent resonance and the photonic bound states lead to the perfect reflection appearing in the incident channel. The fidelity of the atom is related to the magnitude of the coupling strength and can reach unit when the coupling strength matches g _a = g _b . This shows that the transfer of a single photon into another quantum channel has no influence on the fidelity at special points.     

Fermion superfluid with hybridized <Emphasis Type="Italic">s</Emphasis>- and <Emphasis Type="Italic">p</Emphasis>-wave pairings

Ever since the pioneering work of Bardeen, Cooper and Schrieffer in the 1950s, exploring novel pairing mechanisms for fermion superfluids has become one of the central tasks in modern physics. Here, we investigate a new type of fermion superfluid with hybridized s- and p-wave pairings in an ultracold spin-1/2 Fermi gas. Its occurrence is facilitated by the co-existence of comparable s- and p-wave interactions, which is realizable in a two-component ⁴⁰K Fermi gas with close-by s- and p-wave Feshbach resonances. The hybridized superfluid state is stable over a considerable parameter region on the phase diagram, and can lead to intriguing patterns of spin densities and pairing fields in momentum space. In particular, it can induce a phase-locked p-wave pairing in the fermion species that has no p-wave interactions. The hybridized nature of this novel superfluid can also be confirmed by measuring the s- and p-wave contacts, which can be extracted from the high-momentum tail of the momentum distribution of each spin component. These results enrich our knowledge of pairing superfluidity in Fermi systems, and open the avenue for achieving novel fermion superfluids with multiple partial-wave scatterings in cold atomic gases.     

Double-temperature ratchet model and current reversal of coupled Brownian motors

On the basis of the transport features and experimental phenomena observed in studies of molecular motors, we propose a double-temperature ratchet model of coupled motors to reveal the dynamical mechanism of cooperative transport of motors with two heads, where the interactions and asynchrony between two motor heads are taken into account. We investigate the collective unidirectional transport of coupled system and find that the direction of motion can be reversed under certain conditions. Reverse motion can be achieved by modulating the coupling strength, coupling free length, and asymmetric coefficient of the periodic potential, which is understood in terms of the effective potential theory. The dependence of the directed current on various parameters is studied systematically. Directed transport of coupled Brownian motors can be manipulated and optimized by adjusting the pulsation period or the phase shift of the pulsation temperature.     

硅探测器的数字化脉冲形状甄别

介绍了利用硅探测器的脉冲形状甄别进行粒子鉴别的原理。详细叙述了基于数字化方法的脉冲形状甄别的实现。采样频率和位数是数字化方法的两个重要参数。对于硅探测器信号,采用100 MS/s,12 bit的Digitizer可以满足脉冲形状甄别法对时间分辨的要求。同时对该方法粒子鉴别的特征和能量阈值做了简要的分析和对比。粒子背面入射硅探测器的所得的阈值低于正面入射的情况。例如对于氖周围的同位素,背面入射情况的阈值约为100 MeV,为正面入射情况下鉴别阈值的二分之一,相当与ΔE-E方法中ΔE探测器厚度约为60 μm情况下的阈值。最后定性讨论了硅探测器的电阻率不均匀性和沟道效应对粒子鉴别性能的影响。In this paper Pulse Shape Discrimination(PSD) for silicon detector has been briefly introduced. The emerging digital method successfully applied to detector signal processing makes digital PSD method one of the most promising particle identification methods. Sampling frequency and the number of bits are two key parameters of digital method. For silicon detector signal, adopting 100 Ms/s, 12 bit Digitizer can satisfy the time resolution requirement of PSD method. The identification characteristic and energy threshold of this method have been discussed and compared with both front injection and rear injection cases. Energy threshold with rear injection usually is much lower than that with front injection. For example, around for Neon isotope energy threshold with rear injection is about 100 MeV which is only half of the threshold with front injection, also equivalent to thickness of about 60 μm silicon detector threshold in ΔE-E method. At the end the impact of silicon detector's resistivity nonuniformity and channel effect on the identification capacity of PSD method has been discussed in detail.     

High-power CW diode-side-pumped 1341 nm Nd:YAP laser

A high-power CW diode-side-pumped Nd:YAP laser with linearly polarization at 1341 nm has been described. The laser characteristics including thermal lens and stability of flat–flat resonator were studied. By comparing the output powers at different resonator lengths and different output couplers, the c-axis polarized laser working at 1341 nm has been obtained with a maximum output power of 121 W at the pumping power of 555 W. The optical–optical efficiency is 21.8% and the optical slope efficiency is 40%. The a-axis polarized laser at 1339 nm has also been successfully obtained when the c-axis polarized laser had become instable with the increase of pumping power.     

Nd:GGG晶体荧光寿命的测试

针对Nd:GGG激光器,介绍了荧光寿命测试原理,设计了低频窄脉宽荧光寿命测试系统.该系统由光源、光路系统、驱动电路和探测系统等几部分组成.利用脉冲取样技术测试了Nd:GGG晶体的荧光寿命约为250μs左右.     

机械合金化合成CoSb3过程中的固相反应机理的热力学解释

用Co和Sb作为初始原料，通过机械合金化(mechanical alloying, MA)的方法合成了CoSb₃,并系统研究了MA转速和MA时间对MA过程中固相反应的影响.XRD结果表明，相同MA转速下，CoSb₃的量随MA时间的延长而增多，但是MA时间过长会导致大量CoSb₂的生成，甚至诱发CoSb₃分解为CoSb₂和非晶态Sb.而提高MA转速，只能缩短固相反应的发生时间，而不会改变整个固相反应 关键词： 机械合金化 热电材料 3')" href="#">CoSb₃ 非平衡热力学