Dip-coated HNR120 photoresists thin-film optical waveguides

We report on our systematic and detailed study of fabrication and characterization of HNR120 photoresists thin-film optical waveguides. Various waveguide properties, such as refractive index, optical losses as a function of temperature, waveguide thickness, dispersion and birefringence have been studied. The optical loss are found to be <1.4 dB cm⁻¹.     

Ablation of Transparent Materials Using Excimer Lasers for Photonic Applications

For many years, the development of effective ablation or laser machining techniques for making micro-optical components has been the key factor in the birth of new photonic devices and systems. In this article, the ablation characteristics of two types of the most important transparent materials, transparent polymers and glasses, are studied. Simple shaped microcavities are first machined for studying the fundamental ablation parameters, including threshold fluence, effective absorption coefficient, and ablation rate. In studying polymer ablation, five standard grades and five proprietary polymeric compounds are selected. Ablation techniques using these transparent polymers for making arrayed ferrules and curved microlenses are presented. Applications of these ablated microstructures for optical fiber connectors, optical fiber coupling and alignment, and transparent chip encapsulants, are introduced and demonstrated with emphasis on the quality of the ablated profiles and dimensions to satisfy the required performance. In glass ablation, borosilicate glasses are considered and their associated ablation behaviors are studied. The procedures to ablate glass-based arrayed microstructures with flat and curved surfaces are described. The utilizations of these arrayed microstructures for optical waveguide, wave absorber, and beam guider, are specifically discussed. Finally, concluding remakes for future trends are presented.     

用于X射线时空分辨测量的弯晶谱仪

为了测量激光聚变产生的0.2～0.37 nm范围内的等离子体X射线, 设计了一种基于空间和时间分辨的聚焦型弯晶谱仪. 将在700℃时弯曲后的LiF(2d＝0.403 nm)晶体作为色散元件, 布喇格衍射角的变化范围为30～67.5°, 弯晶粘贴在离心率和焦距分别为0.9586和1350 mm的椭圆形不锈钢基底上. 利用弯晶谱仪配X光CCD相机在星光Ⅱ激光(0.35 μm, 60～80J, 700 ps)装置上摄取了钛平面靶发射的X射线光谱, 实验结果表明它的光谱分辨率能达到0.001 nm.     

Transmission Characteristics of 90° Bent Photonic Crystal Waveguides

There are several key factors that affect the transmission characteristics of the 90° (L-shaped) bent photonic crystal waveguides. The first factor is the direct coupling efficiency from the incident lights into the waveguides. The second one is the bandgap deviations of the photonic crystals. And the third factor is the optical reflections in the bent corners. In this article, we compare three types of L-shaped bent photonic crystal waveguides. One is the original type, which has an abrupt right-angle bend. Another is an improved 90° bend with a 45°-mirror. The other is an L-shaped bent photonic crystal waveguide with a 45°-transitional section. We investigate their respective frequency responses and observe the improvements in the total transmission efficiencies provided by the latter types.     

Coupling Fibers to Planar Waveguides Using a High-Temperature Epoxy

Computer simulation was used to understand the adhesive-based coupling of optical fibers to planar waveguides with a view to adhesive development. Satisfactory coupling performance could be achieved with facet-angled fibers and waveguides, regardless of the adhesive's index and optical loss. A high-temperature epoxy adhesive was developed for coupling applications based on the simulation. The adhesive is able to achieve a material-related loss of -0.05 dB and a back-reflection loss of less than -50 dB in the coupling. In addition, the adhesive has excellent mechanical and thermal properties and can easily meet the Telcordia standard GR1221 while withstanding high temperatures and high optical power.     

Critical ray-like propagation modes along graded-index planar optical waveguides

Graded-index planar optical waveguides and surface compression layers were formed simultaneously in the surface layer of glass plates by ion exchange. A change in the refractometer patterns was observed. Before ion exchange, only a critical ray fringe was observed, but with ion exchange a guided wave fringe appeared on the high effective refractive index side of the ‘critical ray’ fringe, and the number of guided wave fringes increased. The guided wave fringe or fringes were birefringent, whereas the ‘critical ray’ fringe was kept nonbirefringent. It was concluded that the ‘critical ray’ propagated along the bottom of a waveguide, ie at the foot of the refractive index distribution.     

Mode structure in wideband waveguide radiofrequency CO2 lasers

We have analysed the mode structure of a wideband radiofrequency excited waveguide CO₂ laser by using different waveguide diameters and optical cavities. In particular we have observed the phase shift of some linear polarized waveguide modes in the transition region between the guided and the free Gaussian propagation.     

分层复合材料光波导的非线性二次增强效应

通过对分层复合材料光波导ＴＭ模等效介电系数的分析，清楚地预言了无限扩展分层复合材料结构中的非线性增强将因光波导的边界作用而引起进一步的加强。     

矩形截面多量子阱脊形波导模式特性

本文根据多量子阱双折射率的性质,运用有效折射率法分析了矩形截面多量子阱脊形波导E_mn^x模和模E_mn^y的模式特性。     

A proposed method for generating and receiving narrow beams of ultrasound in the Fast Reactor liquid sodium environment

In the liquid sodium coolant of the Fast Reactor there are several measurements which may be performed using ultrasonic techniques. This paper gives a brief outline of one such measurement and then describes the design of an ultrasonic waveguide for the generation and detection of ultrasound in this hostile situation. The successful laboratory tests of the device are also reported.