掺稀土光纤的光子暗化研究进展

掺稀土光纤是光纤激光器的基础,而掺杂光纤的光子暗化是影响激光输出功率稳定性的重要因素。综述了光子暗化的产生机理、光子暗化对光纤激光器的影响及其抑制方法,旨在为相关研究提供参考。     

Acylstannanes: Cleavable and Highly Reactive Photoinitiators for Radical Photopolymerization at Wavelengths above 500 nm with Excellent Photobleaching Behavior

Within this work, a novel acylstannane‐based photoinitiator (PI) is presented. Tetrakis(2,4,6‐trimethylbenzoyl)stannane ( 1 ) displays outstanding properties compared to state‐of‐the‐art acylgermane‐based initiators. Most importantly, the initiator shows absorption up to 550 nm, which allows higher penetration depths, especially in highly filled photopolymers. Besides that, 1 shows extremely high photoinitiating activity towards (meth)acrylic double bonds, as well as very fast photobleaching. Furthermore, unlike many organotin compounds, 1 shows surprisingly low cytotoxicity.     

Single-molecule surface- and tip-enhanced raman spectroscopy

A review is given on single-molecule surface- and tip-enhanced Raman spectroscopy (SERS and TERS). It sketches the historical development along different routes toward huge near-field enhancements, the basis of single-molecule enhanced Raman spectroscopy; from SNOM to apertureless SNOM to tip-enhanced Raman spectroscopy (TERS) and microscopy; from SERS to single-molecule SERS to single-molecule TERS. The claim of extremely high enhancement factors of 10¹⁴ in single-molecule SERS is critically discussed, in particular in the view of recent experimental and theoretical results that limits the electromagnetic enhancement to ? 10¹¹. In the field of TERS only very few reports on single-molecule TERS exist: single-molecule TERS on dyes and on a protein (cytochrome c). In the latter case, TERS ‘sees’ even subunits of this protein, either amino-acids or the heme, depending on the orientation of the protein relative to the tip. The former case concerns the dye brilliant cresyl blue adsorbed either on a Au surface under ambient conditions or on a Au(111) surface in ultra high vacuum. These results indicate that significant progress is to be expected for TERS in general and for single-molecule TERS in particular.     

A novel photobleachable polysilane copolymer for optical waveguide fabrication

Poly(methylphenylsilane)‐poly(benzylmethacrylate) (PMPS‐PBzMA) block copolymer was prepared by photopolymerization of benzylmethacrylate (BzMA) monomer using PMPS as a macromolecular photo‐radical initiator. Its application as a photobleachable polymer material for optical waveguide fabrication was investigated. By changing weight ratios of BzMA to PMPS during polymerization, the obtained PMPS‐PBzMA showed different photo‐induced refractive changes. PMPS‐PBzMA proved to have good photosensitivity, optical properties, and thermal stability. A multimode PMPS‐PBzMA optical waveguide was achieved, with a propagation loss of 1.0 dB/cm at 1310 nm. Copyright © 2009 John Wiley & Sons, Ltd.     

W-红色素的光褪色研究

红曲色素在自然光的作用下会逐渐褪色,紫外线是自然光中引起有机物褪色的主要光线。为了探明红曲色素光照褪色的机理,采用紫外灯照射一种红曲红色素(分子式C19H28N2O5)的水溶液至无色,经红外光谱、质谱和核磁图谱分析,鉴定其褪色后物质的分子式为C14H9NO6。根据光化学理论分析,提出了红曲红色素的光褪色机理:在紫外光作用下,红曲红色素分子中的脂肪族侧链首先在α-碳原子处发生NorrishⅠ型断裂,成为自由基,随后在碳7位甲基上发生相同反应,接着色素发生电子转移,双键转换,水溶液中产生羟自由基、超氧阴离子等自由基,与色素结构中双键发生加成反应,共轭双键消失,色素失去颜色。防止红曲红色素光褪色应首先考虑稳定其脂肪族侧链结构,其次可以在色素中添加自由基清除剂。     

光漂白引起推拉型偶氮有机聚合物折射率变化的测量

本文主要研究了聚合物材料漂白引起的年射率变化的测量方法。通过光漂白在薄膜上形成折射率减小的区域,用探测光对该区域进行单光束扫描,由测量的归一化透过率得到薄膜的折射率变化。在实验上测量出了用Ar^ 激光作为漂白光源时6种系列偶氮化合物掺杂聚合物薄膜的折射率变化,实验结果具有较高的精确度。     

Novel Photobleachable Deep UV Resists Based on Single Component Nonchemically Amplified Resist System

Summary: Photobleachable deep UV resists were designed by introducing diazoketo groups in polymer side chains. The diazoketo groups undergo the Wolff rearrangement upon irradiation in the deep UV, affording ketenes that react with water to provide base‐soluble photoproducts. The polymers were synthesized by radical copolymerization of 2‐(2‐diazo‐3‐oxo‐butyryloxy)‐ethyl methacrylate, 2‐hydroxyethyl methacrylate, and γ‐butyrolacton‐2‐yl methacrylate. The single component resist showed 0.7 µm line and space patterns using a mercury‐xenon lamp in a contact printing mode.

Scanning electron micrograph of 0.7 µm line and space patterns printed with polymer B at a dose of 70 mJ · cm⁻².