激光诱导下Yb—Ba间的能量转移过程

本文研究了在激光诱导下Ba和Yb的两对非偶极允许能级间的碰撞能量转移,得到了转移截面与诱导激光波长的关系。观察到自旋相互作用对它的影响。 关键词：     

反斯托克斯喇曼激光

人们对发展紫外及真空紫外波段的激光器 十分重视.其主要原因是它在凝聚态物理、原 子和分子物理、光化学及半导体工业上有着广 泛的应用. 强激光在非线性晶体和原子蒸气中高次谐波的产生以及混频过程是获得短波辐射的一个 重要途径.但这些过程的截面一般都相当小, 限制了短波长辐射产生的效卒. 近年来,用原子的亚稳能级和基能级之间的反斯托克斯喇曼散射得到了相当强的紫外受激辐射.这个过程如图1所示.图中的a,b,c表示原子能级,其中b,a是喇曼散射的上、下能级,c是可能的中间能级.　　p是诱导光频率,　　As是反斯托克斯喇曼频率.当b相对于a…     

中功率染料激光器

本文报道一台供光谱研究用的染料激光装置.它使用倍频Nd:YAG激光激励,输出功率大于500kw,线宽为0.03A,光谱亮度达1.6×10～7W/A.国内外作者均进行过研制[1,2] 装置光路如图1所示,它由振荡器和一级放大器组成,泵光源使用北京无线电工具设备厂生产的T-49-ZE倍频Nd:YAG激光器.振荡     

STUDY ON LIGHT LOCALIZATION OF ONE-DIMENSIONAL DISORDERED MULTILAYER

Antimonite and cryolite are used as the high and low refractive index coating materials to be evaporated alternately to the glass substrates. All cryolite layers have the same thickness d/4n_a, and the thickness of antimonite layers varies randomly around an average value d/4n_b, with d=650nm, n_a and n_b their refractive indices. Three kinds of multilayer are prepared, they possess the same degree of thickness disorder, but different total lengths, i.e., 10, 15 and 21 perioda. We measure the transmission and reflection spectrum after the light passing through these multilayers. The exponential intensity variation versus total length is experi-mentally demonstrated, and the light localization length is then obtained. Our experimental results can be fitted very well with the numerical simulation. Based on the measured and calculated localization length, the effects of phase coherent: Bragg reflection and Anderson localization are discussed.     

Measurements of displacement and trapping force on micron-sized particles in optical tweezers system

A high-stability optical tweezers equipped with a high-precision measurement system of displacement and force is set up. The results show that this combination can be used to carry out quantitative measurements of small displacements and forces for micron-sized spheres. The precision of measurements has reached nanometers and piconewtons, respectively.     

Theoretical study of enhancement and suppression of the fluorescent spectra of dye molecules in a photonic crystal with a pseudogap

We have investigated the analytical forms of the photonic density of states (DOS) in a photonic crystal in the interested frequency regime according to the rule of state conservation in a photonic crystal with pseudogaps, which states that, if a valley of the DOS appears in some range of frequencies, it must be compensated for by increasing over some other ranges. By using a model DOS with a state-conservative photonic pseudogap, we have also investigated the enhancement and suppression of spontaneous emission of two-level atoms with different frequency positions and widths of emission spectra in a state-conservative electromagnetic reservoir; and the DOS-induced suppression, enhancement, narrowing and redshifting or blueshifting of spontaneous emission spectra are naturally obtained.     

利用二维光子晶体提高波的耦合效率

通过多重散射方法数值模拟研究和实验测量表明利用二维光子晶体可以提高波的耦合效率.研究发现,高的波耦合效率通常发生在光子禁带的边沿和其它非禁带区的某些频率处.当光子晶体的晶格常数接近于所传输的波的波长时,会出现很高耦合效率的共振耦合现象.利用二维光子晶体的情况下的波耦合效率最高可以达到不利用二维光子晶体时的1.89倍.这种现象在光集成器件中尤其有用.     

Controlling the focusing properties of a triangular-lattice metallic photonic-crystal slab：

This paper studies the focusing properties of a two-dimensional photonic crystal (PC) slab consisting of a triangular lattice of metallic cylinders immersed in a dielectric background. Through the analysis of the equifrequency-surface contours and the field patterns of a point source placed in the vicinity of the PC slab, it finds that both the image distance and image quality can be controlled by simply adjusting the refractive index of the background material.     

Near-field imaging of a square-lattice metallic photonic-crystal slab at the second band

Imaging properties of a two-dimensional photonic crystal slab lens are investigated through the finite-difference time-domain method. In this paper, we consider the photonic crystal slab consisting of a square lattice of square metallic rods immersed in a dielectric background. Through the analysis of the equifrequency-surface contours and the field patterns of a point source placed in the vicinity of the photonic crystal slab, we find that a good-quality image can form at the frequencies in the second TM-polarized photonic band. Comparing the images formed at different frequencies, we can clearly see that an excellent-quality image is formed by the mechanisms of simultaneous action of the self-collimation effect and the negative-refraction effect.     

Optical properties of the direct-coupled Y-branch filtersby using photonic crystal slabs

We fabricated a new type of two-dimensional photonic crystal slab filter. The resonant cavities were directly put into the waveguide arms. The optical transmissions of the filters were measured and the results show that the optimized two-channel filters give good intensity distribution at the output ports of the waveguide. A minimum wavelength spacing of 5~nm of the filter outputs isrealized by accurately controlling the size of the resonant cavities.