KrF激光脉冲整形研究

 实验研究了脉冲堆积法对KrF激光的整形能力。利用受激布里渊散射(SBS)压缩脉冲获得了脉宽为3~5 ns的短脉冲，用4束激光堆积获得了脉宽为10~15 ns、平顶宽度为5~10 ns的整形脉冲。利用实测SBS脉冲数据，对脉冲堆积法进行了数值模拟，模拟的脉冲宽度为12.7 ns，平顶宽度为7.7 ns，该结果与实验相符。对脉冲堆积法的任意整形能力进行了模拟，讨论了脉冲宽度变化对整形的影响，发现脉宽变化在5%以内时，对整形脉冲的影响较小。对整形脉冲的放大进行了定性研究，结果表明：平顶脉冲通过放大器后，前沿部分放大较多，由于饱和作用，后沿放大较少；如果前端整形脉冲前沿为斜坡状，放大后可以得到近平顶的脉冲。     

用于光纤拉曼放大器抽运源的单级光纤拉曼激光器

抽运光源是光纤拉曼放大器应用于密集波分复用系统的关键技术,设计了一种紧凑型的808nm激光二极管抽运的基于钒酸钇（Nd^3＋：YVO4）晶体1342nm固体激光器模块,提出利用上述1342nm固体激光器抽运基于光纤光栅的单级全光纤型拉曼谐振器获得1．4μm激光输出的光纤拉曼激光器,分析了固体激光器的阈值特性、性能优化方法和单级光纤拉曼谐振器的设计方法。上述1342nm固体激光器模块在抽运功率2W时获得了最大655mW的激光输出功率和42．6％的斜率效率,单级拉曼谐振器的1342nm到1．4μm光功率转换斜率效率达75％,在1425nm、1438nm、1455nm和1490nm处的输出功率达到300mW以上。最后给出基于1．4μm光纤拉曼激光器抽运的宽带平坦放大的光纤拉曼放大器的结构参量和性能测试结果。     

15波长输出的布里渊掺铒光纤激光器

多波长布里渊掺铒光纤激光器是一种新型的多波长光纤激光器,其原理是利用受激布里渊增益和掺铒光纤的线性增益,可以在常温下得到波长间隔约为0．08nm(～10GHz)的多波长输出。报道的布里渊掺铒光纤激光器,在布里渊抽运功率为1．7mW、980nm抽运功率为300mW的情况下得到稳定的15个波长(间隔～10GHz)的输出,这种激光器用作光传感器、光谱分析仪以及密集波分复用系统的光源。实验发现,输出波长的个数随着980nm抽运功率的增大而增加。另外,布里渊掺铒光纤激光器的信号功率主要来自于掺铒光纤的增益,而布里渊增益对它的影响不大。     

Determination of bulk viscosity of liquid water via pulse duration measurements in stimulated Brillouin scattering

We present a method by which to determine the bulk viscosity of water from pulse duration measurements of stimulated Brillouin scattering （SBS）. Beginning from a common model of Brillouin scattering, the bulk viscosity is shown to play an important role in Brillouin linewidth determination. Pulse durations of SBS back-reflected optical pulses are measured over the temperature range of 5-40℃. SBS linewidths are de- termined via Fourier transformation of the time-domain results, and the bulk viscosity of water is measured and derived from the obtained values. Our results show that the proposed method for measurement of pulse durations is an effective approach for determining bulk viscosity. The method can be easily extended to determine bulk viscosities of other Newtonian liquids.     

受激Raman谱中的宏观极化干涉

研究了Rb⁸⁵原子蒸气D1线系统中的受激Raman增益与损耗现象. 实验中观察到 随着抽运光失谐量的增大, 受激Raman谱明显地呈现出一个从增益到损耗的陡峭转变. 从缀饰态模型出发, 我们提出这是对探测光有相反贡献的不同速度原子群之间极化干涉的结果. 关键词： 受激Raman谱 电磁感应透明 极化干涉     

Metallic nanowires for subwavelength waveguiding and nanophotonic devices

Plasmonics is a rapidly developing field concerning light manipulation at the nanoscale with many potential applications, of which plasmonic circuits are promising for future information technology. Plasmonic waveguides are fundamental elements for constructing plasmonic integrated circuits. Among the proposed different plasmonic waveguides, metallic nanowires have drawn much attention due to the highly confined electromagnetic waves and relatively low propagation loss. Here we review the recent research progress in the waveguiding characteristics of metallic nanowires and nanowire-based nanophotonic devices. Plasmon modes of both cylindrical and pentagonal metallic nanowires with and without substrate are discussed. Typical methods for exciting and detecting the plasmons in metallic nanowires are briefly summarized. Because of the multimode characteristic, the plasmon propagation and emission in the nanowire have many unique properties, benefiting the design of plasmonic devices. A few nanowire-based devices are highlighted, including quarter-wave plate, Fabry-Prot resonator, router and logic gates.     

Investigations of ionization-induced injection of laser wake field acceleration using phenomenological model

We develop a phenomenological model to investigate dynamics of ionization-induced injection. In the ＂bubble＂ regime of laser wakefield acceleration （LWFA）, it is found that there is an upper limit for laser intensity of ionization-induced injection. In the plane perpendicular to the laser polarization, when the laser pulse is linearly polarized, ionization-induced injected electrons exhibit a filamented structure and semi-coherent betatron oscillation.     

Rainbow trapping based on long-range plasmonic Bragg gratings at telecom frequencies

The group velocity of long-range surface plasmon polaritons (LRSPPs) in a wide frequency bandwidth at infrared frequencies is significantly reduced by dielectric gratings of graded thickness on both sides of a thin metal film. This structure can reduce the propagation loss of slow surface plasmons in rainbow trapping systems based on plasmonic Bragg gratings. Compared with dielectric gratings of graded thickness on a single side of a metal film, the proposed structure is able to guide slow light with a much longer propagation distance for the same group index factor. Finite- difference time-domain simulation results show that slow LRSPPs with the group velocity of c/14.5 and the propagation distance of 10.4 μm are achieved in dielectric gratings of uniform thickness on both sides of a thin metal film at 1.62 μm.     

激基复合物给体作间隔层对激子复合区域的调节

为研究激基复合物器件激子复合区域的变化,在TPD/BPhen界面可形成激基复合物发光的基础上,以Ir(pq)2(acac)为探测层,制备器件ITO/Mo O_3(2.5 nm)/TPD((40-x)nm)/Ir(pq)2(acac)(0.5 nm)/TPD(x,x=0,3,6,10 nm)/BPhen(40 nm)/Cs2CO_3/Al,其中靠近BPhen的TPD称之为间隔层。电致发光光谱表明,该组器件的激子复合区域主要位于Ir(pq)2(acac)薄层和TPD/BPhen界面,分别发射595 nm和478 nm的光。随着TPD间隔层厚度的增加和电压的升高,发光区域向激基复合物区域(TPD/BPhen界面)移动,即更多的电子和空穴在TPD/BPhen界面形成激基复合物发光,Ir(pq)2(acac)发光减弱。当间隔层厚度由0 nm增至10nm时,6 V电压下的Ir(pq)2(acac)和激基复合物发光强度的比值由44降至1.5。对于间隔层厚度为6 nm的器件,Ir(pq)2(acac)和激基复合物发光强度的比值由6 V时的2.8降至10 V时的1.0。由此可见,激基复合物给体作间隔层能有效调节激子复合区域。