单光子态的产生与测量

报道了通过自发参量下转换产生单光子态的实验研究,使用中心波长425 nm的飞秒脉冲泵浦Ⅰ类非共线相位匹配的BBO晶体,在实验上得到单光子计数率为2.978×10-4,并分析了实验中的相关问题.     

Rheooptical investigation of the crystallization of poly(ethylene terephthalate) under tensile strain

The crystallization of poly(ethylene terephthalate) under uniaxial tensile strain at different extension rates was investigated with optical polarimetry in a temperature range between the glass-transition temperature and the quiescent crystallization temperature. The evolution of the optical properties of the polymer, including the turbidity, birefringence, and dichroism, were monitored simultaneously with the mechanical parameters. To complete the semicrystalline microstructure characterization of the polymer under strain, an online wide-angle X-ray diffraction (WAXD) technique was used in separate experiments, which were performed under the same thermomechanical conditions. For real-time measurements, a high-energy synchrotron radiation source was used. The optical properties provided information about both the crystalline and amorphous phases, whereas the WAXD patterns essentially gave information about the crystalline phase. The two experimental techniques were then used in a complementary way to characterize the semicrystalline microstructure. Significant deviations from the stress-optical rule were found. This was attributed to both transient effects and the appearance of crystallites, which consisted of highly oriented molecular segments that could contribute to the optical anisotropy but not necessarily to the stress. The behavior of the optical dichroism was found to be qualitatively different from that of the birefringence. The latter monotonically increased with the strain, whereas the former first increased with the strain, passed through a maximum, and then decreased to a steady-state value. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 1915–1927, 2004     

Stability control of the electrooptic effect with new maleimide copolymers containing photoreactive tricyanopyrrolidene‐based chromophores

New photocrosslinkable maleimide copolymers have been synthesized by the attachment of a tricyanopyrrolidene‐based chromophore. The 2‐(3‐cyano‐4‐(2‐{4‐[hexyl‐(6‐hydroxy‐hexyl)‐amino]‐phenyl}‐vinyl)‐5‐oxo‐1‐{4‐[4‐(3‐oxo‐3‐phenyl‐propenyl)‐ phenoxy]‐butyl}‐1,5‐dihydro‐pyrrol‐2‐ylidene)‐malononitrile chromophore exhibits nonlinear optical activity and contains a chalcone moiety that is sensitive to UV light (λ = 330–360 nm) for crosslink formation. The maleimide monomers have also been functionalized with chalcone moieties. The resultant copolymers exhibit great processability, and one of them shows a maximum electrooptic coefficient of 90 pm/V at 1300 nm. We could control the thermal stability of the electrooptic coefficient with the newly synthesized photoreactive copolymers successfully. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 531–542, 2007     

Synthesis and characterization of meso-ferrocenylethynyl 5,15-diphenylporphyrins

A series of four meso-ferrocenylethynyl (5,15-diphenylporphyrinato)nickel(II) derivatives have been synthesized by Sonogashira coupling reactions. Three of these compounds contain the electron-withdrawing groups including -CHO, -CHC(CN)₂, and -CCC₆H₄NO₂ at the remaining meso position, with a view to preparing push-pull chromophores, in which ferrocene serves as the electron donor. All the new compounds have been characterized spectroscopically and the molecular structure of one of these porphyrins (compound 11) has also been determined. The studies show that although the ferrocenylethynyl group can extend the π system of the central porphyrin core, the cyclopentadienyl rings of ferrocene are almost orthogonal to the porphyrin ring. This hinders ferrocene serving as a good electron donor in these systems.     

Quarter wave plates for submillimeter wavelengths

A review is given of different types of quarter wave plates as presently used in the optical and microwave spectral range, with a view to their application in the sub-mm wave-length range. Two types of quarter wave plates have been constructed and results of measurements at 640m are given.     

级联二阶非线性铌酸锂全光开关的研制

以基于准位相匹配和频与差频级联二阶非线性[X^(2)：X^(2)]基础上的全光开关的理论分析作指导,进行了周期极化铌酸锂晶体(PPLN)和退火质子交换光波导(APE)的实验制备,利用所研制的PPLN-APE器件,以自行研制的工作波长为1．54μm的被动调Q掺钴铝酸镁激光器作为控制光源,以工作波长为1．5μm的连续二极管激光器为信号光源进行了级联二阶非线性全光开关实验。当控制光峰值功率为3kw,信号光功率为1mW时,实现13％的开关效率,分析了进一步提高全光开关性能的途径。     

Multi-State Second-Order Nonlinear Optical Switches Incorporating One to Three Benzazolo-Oxazolidine Units: A Quantum Chemistry Investigation

This contribution employs quantum chemistry methods to describe the variations of the second nonlinear optical responses of molecular switches based on benzazolo-oxazolidine (BOX) units, connected by π-linkers, along their successive opening/closing. Under the fully closed forms, all of them display negligible first hyperpolarizability (β) values. When one BOX is opened, which is sketched as C→O, a push–pull π-conjugated segment is formed, having the potential to enhance β and to set the depolarization ratio (DR) to its one-dimensional-like value (DR = 5). This is observed when only one BOX is open, either for the monoBOX species (C→O) or for the diBOX (CC→CO) and triBOX (CCC→CCO) compounds, i.e., when the remaining BOXs stay closed. The next BOX openings have much different effects. For the diBOXs, the second opening (CO→OO) is associated with a decrease of β, and this decrease is tuned by controlling the conformation of the π-linker, i.e., the centrosymmetry of the whole compound because β vanishes in centrosymmetric compounds. For the triBOXs, the second opening gives rise to a Λ-shape compound, with a negligible change of β, but a decrease of the DR whereas, along the third opening, β remains similar and the DR decreases to the typical value of octupolar systems (DR = 1.5).     

Scattering Matrix Modeling of Photon Migration in Turbid Media

Ｉｎｔｒｏｄｕｃｔｉｏｎ　　Ｏｐｔｉｃａｌｔｏｍｏｇｒａｐｈｙｕｓｉｎｇｎｅａｒｉｎｆｒａｒｅｄｌｉｇｈｔｔｏｅｘｔｒａｃｔｉｎｔｅｒｉｏｒａｂｎｏｒｍａｌｉｔｉｅｓｉｎｆｏｒｍａｔｉｏｎａｔｔｒａｃｔｓｍａｎｙｒｅｓｅａｒｃｈｉｎｔｅｒｅｓｔｓｉｎｂｉｏｍｅｄｉｃａｌｏｐｔｉｃｓ［１］,ｂｅｃａｕｓｅｉｔｐｒｏｖｉｄｅｓａｎａｌｔｅｒｎａｔｉｖｅｐｏｔｅｎｔｉａｌｍｏｄａｌｉｔｙｔｏｐｒｏｂｅｂｒｅａｓｔｃａｎｃｅｒａｎｄｍｏｎｉｔｏｒｂｒａｉｎａｎｄｍｕｓｃｌｅｏｘｙｇｅｎａｔｉｏｎｎｏｎ…     

Light level control in birefringent fibres through thermal stress effects caused by the absorption of broadside incident light: a single-ended fibre-optic system

In this paper, light level control is demonstrated using optically induced thermal stress effects in a polarization-maintaining optical fibre. The controlling light beam is absorbed by a blackened segment of the fibre and produces local heating. Light control is demonstrated in the single-ended sensor configuration, which displays a response that cannot be explained from phase delays only, but requires the addition of the coupled mode theory.     

机载激光海深勘测系统的发展

机载激光海洋测深系统对快速而便宜地绘制沿海海图和探测潜艇有重要意义。本文综述该系统的优缺点、工作原理及研制状况。