Studies on the SFD Properties of Nd_xGd_(1-x)Ca_4O(BO_3)_3 Solid-solution Crystal

1　Ｉｎｔｒｏｄｕｃｔｉｏｎ　　Ｉｎｔｈｅｐａｓｔｆｅｗｙｅａｒｓ,ｓｍａｌｌｓｉｚｅｄＳＦＤｌａｓｅｒｈａｓａｔｔｒａｃｔｅｄｇｒｅａｔａｔｔｅｎｔｉｏｎｓ.Ｌａｓｅｒｄｉｏｄｅ(ＬＤ)ｐｕｍｐｅｄｓｏｌｉｄｓｔａｔｅｌａｓｅｒｓｈａｖｅｂｅｅｎｆｏｕｎｄｖｅｒｙｕｓｅｆｕｌｉｎｔｈｅｆｉｅｌｄｓｏｆｍｉｌｉｔａｒｙ,ｉｎｄｕｓｔｒｙ,ｍｅｄｉｃａｌｔｒｅａｔｍｅｎｔａｎｄｓｃｉｅｎｔｉｆｉｃｒｅｓｅａｒｃｈｅｓｄｕｅｔｏｔｈｅａｄｖａｎｔａｇｅｓｏｆｈｉｇｈｓｔａｂｉｌｉｔｙ,ｃｏｍｐａｃｔｎｅｓｓ…     

Studies on the SFD Properties of NdxGd1-xCa4O(BO3)3 Solid-solution Crystal

NdxGd1-xCa4O(BO3)3 (NdGdCOB) is a new self-frequency-doubling (SFD) solid-solution crystal. The second-harmonic generation (SHG) phase-matching (PM) curves were calculated by using refractive indices. The deff of NdGdCOB crystal along different PM directions were calculated according to the sellmeier equation and dijk data in which the (θ=66.8°, φ=132.6°) PM direction has the highest deff. SFD experiments were carried out with Ti:sapphire CW laser and pulsed dye-laser. A green laser output power up to 225 mW at 530 nm was achieved from a 7×3×3 mm3 crystal sample pumped by 1560 mW CW Ti:sapphire laser. The lasing threshold of SFD was lower than 1.8 mW along the PM direction (66.8°,132.6°). The optical-optical conversion efficiency was 14.4%. The conversion efficiency was 7.7% when 10×3×3 mm3 sample was side-pumped by the pulsed dye-laser tuned to 595.4 nm with 17.5 mJ energy and the lasing threshold is 1.2 mJ.     

Novel MEMS variable optical attenuator

A novel MEMS variable optical attenuator (VOA), which has completely different attenuation mechanism from those in literatures, is proposed and demonstrated in this paper. The basic operation principle is that the optical power coupled between two initially aligned single-mode fibers will be continuously attenuated while the end of one of the fibers is deflected from the initial position. A micromachined solenoid type inductor with a U-shaped permalloy magnetic core is used to attract the deflectable fiber that has a permalloy coat on its end. To fabricate the multi-layer three-dimensional inductive component, a new UV-LIGA process for thick photoresists is developed, combining advantages of both SU-8 and AZ-4000 series photoresists. The inductive component is approximately 1.7 mm×1.3 mm×50μm in size and has a low resistance value (- 2.1Ω). The whole size of the VOA before packaging is 30 mmx2 mmx0.6 mm. The first prototype shows less then 3-dB insertion loss at 0-dB attenuation and nearly 40-dB att     

Fiber Optic Coupling of CW Linear Laser Diode Array

Based on a set of microoptics the output radiation from a continuous wave (CW) linear laser diode array is coupled into a multi-mode optical fiber of 400 μm diameter.The CW linear laser diode array is a 1 cm laser diode bar with 19 stripes with 100 μm aperture spaced on 500 μm centers.The coupling system contains packaged laser diode bar,fast axis collimator,slow axis collimation array,beam transformation system and focusing system.The high brightness,high power density and single fiber output of a laser diode bar is achieved.The coupling efficiency is 65% and the power density is up to 1.03×104 W/cm2.     

Fiber Optic Coupling of CW Linear Laser Diode Array

1　Ｉｎｔｒｏｄｕｃｔｉｏｎ　　Ｌａｓｅｒｄｉｏｄｅａｒｒａｙ (ＬＤＡ )ｔｈａｔｈａｓｍｕｌｔｉｐｌｅｅｍｉｔｔｉｎｇｒｅｇｉｏｎｓｉｓａｐｅｒｆｅｃｔｄｅｖｉｃｅｔｏａｃｈｉｅｖｅｈｉｇｈｅｒｐｏｗｅｒｏｕｔｐｕｔｓｗｉｔｈａｎｉｎｃｒｅａｓｅｄｂｒｉｇｈｔｎｅｓｓ.ＴｈｅｈｉｇｈＣＷ ｐｏｗｅｒ ,ｈｉｇｈｂｒｉｇｈｔｎｅｓｓａｎｄｆｉｂｅｒｏｕｔｐｕｔｏｆａｌａｓｅｒｄｉｏｄｅｂａｒｃａｎｂｅａｐｐｌｉｅｄｉｎｍｅｄｉｃｉｎｅ ,ｍａｔｅｒｉａｌｓｐｒｏｃｅｓｓｉｎｇ ,ｓｏｌｉｄ ｓｔａｔｅｌａｓ…     

光纤中基于互相位调制效应的超短光脉冲对的产生

提出一种在单模光纤正常色散区由连续波产生超短光脉冲对的新方法.即让连续波和一个波长位于光纤负色散区的高阶孤子在光纤中同时传输,互相位调制效应和群速度色散效应的互相作用能使连续波演化成超短光脉冲对.本文还通过计算机模拟,对该方法进行了全面的考察和分析.结果表明,此方法实用且效果较好.     

Eyewear-style three-dimensional endoscope derived from microstructured polymer fiber with the function of image transmission

A method of fabricating multi-core polymer image fiber is proposed.Image fiber preform is fabricated by stacking thousands of polymer fibers each with a 0.25-mm diameter orderly in a die by only one step.The preform is heated and stretched into image fiber with an outer diameter of 2mm.Then a portable eyewear-style three-dimensional(3D) endoscope system is designed,fabricated,and characterized.This endoscopic system is composed of two graded index lenses,two pieces of 0.35-m length image guide fibers,and a pair of oculars.It shows good ?exibility and portability,and can provide the depth information accordingly.     

High power laser operation with crystal fibers

We present the very last results on the development of high-power lasers with crystal fibers in Nd:YAG and in Yb:YAG grown by the Micro-Pulling Down technique. An overview of the main optical properties of the grown crystal fibers is given as well as the principles of the diode-pumped systems are developed. The average output power obtained with those materials reaches now several tens of watts in the CW regime and in high repetition rate Q-switched operation. Pulses with an energy of several millijoules have been obtained with pulse durations from 10 to 20 ns and peak powers from 100 kW to 350 kW. In each case, the measured M ² quality factors remained in the range 2.5 to 5. In addition, the first demonstration of high-power laser emission with an Yb:YAG crystal fiber of 0.4 mm in diameter is reported. In this case, we obtained an output power of 27 W at 1030 nm under 100 W of pump power at 940 nm in CW regime. To our knowledge, those results represent the highest powers ever generated with crystal fibers obtained directly from the growth. We finally conclude this work by exposing the potential of crystal fiber lasers for a new generation of high-power laser systems.     

回音壁模式光纤激光器的阈值特性研究

研究了一种新型光纤激光器——消逝波激励的回音壁模式光纤激光器的阈值特性.将不同直径的石英光纤分别浸入低折射率的罗丹明6G乙醇和乙二醇混合溶液中,采用沿光纤轴向光抽运消逝波激励染料增益的方式,发现回音壁模式光纤激光辐射的阈值能量和混合溶液的折射率存在不同的依赖关系.随折射率的增加,对小直径光纤,阈值能量随之增加;对大直径光纤,阈值能量单调缓慢递减;对直径适中的光纤,阈值能量先减后增,存在一个和最小阈值能量对应的最佳折射率.用消逝波激励的回音壁模式激光理论,导出了回音壁模式光纤激光的阈值能量公式.理论计算曲线 关键词： 光纤激光器 回音壁模式 激光阈值 消逝波     

石英玻璃微球吸收光谱上的结构共振

通过CO2激光器熔融不同直径的熔锥光纤以得到相应直径的石英玻璃微球,利用此微球和熔锥光纤,构造了球微腔耦合系统。实验中利用光腰直径为3.1μm的熔锥光纤与直径为143.1μm的石英玻璃微球进行耦合,通过最大分辨力为1pm的可调谐半导体激光器对该耦合系统进行光谱扫描,发现石英玻璃微球的吸收光谱中出现分立的结构共振峰。利用光学微球腔理论讨论了石英玻璃微球吸收光谱中的结构共振,并用米氏散射理论公式对一阶TE模共振峰的位置以及它们的间隔进行了计算,共振峰位置实验结果与理论结果的误差仅为0.03%,表明实验与计算结果相符。     

Minimization of Diffraction Losses in Big Gaps of Multi-Mode Waveguides

A systematic approach to design of low-loss miter bends and quasi-optical gaps in multi-mode waveguides is proposed. Several examples illustrate the approach. A mode filter based on a quasi-optical gap in the 31.75 mm diameter corrugated waveguide at frequency 84 GHz has been tested in low (mW) and high-power (200 kW, CW) experiments.     

Eyewear-style three-dimensinal endoscope derived from microstructured polymer fiber with function of image transmission

A method of fabricating multi-core polymer image fiber is proposed. Image fiber preform is fabricated by stacking thousands of polymer fibers each with a 0.25-mm diameter orderly in a die by only one step. The preform is heated and stretched into image fiber with an outer diameter of 2 mm. Then a portable eyewear-style three-dimensional (3D) endoscope system is designed, fabricated, and characterized. This endoscopic system is composed of two graded index lenses, two pieces of 0.35-m length image guide fibers, and a pair of oculars. It shows good flexibility and portability, and can provide the depth information accordingly.     

Creep deformation measurement using quartz optical fiber

This paper describes an optical system for high temperature creep strain measurement using quartz optical fiber, super long working distance microscope and digital image processing techniques. In this system one end of the quartz optical fibers is arrayed in a small area on the specimen surface and the other end is illuminated by a laser beam. The fiber ends on the specimen surface form the spot array. The small optical spots on the specimen are tracked by a CCD camera and the images are processed by digital image processing software. The diameter of each quartz fiber is 100 μm and the fibers can be arrayed in a small area. The local strains are determined by measuring the variety of relative distance between two spots. Experimental results of local creep strain on the welding joints of 15CrMo and HK40 at 850°C are obtained.     

A guided wave monolithic resonator ruby fiber laser

Single crystal ruby fibers, cooled with liquid nitrogen, have been operated as end pumped lasers. The fiber laser is a guided wave device with a length of 15 mm and a mean diameter of 60 μm. The laser resonator structure is monolithic, consisting of an aluminium mirror coated on one fiber end face and an uncoated opposite end face serving as an output coupler. Using an argon ion laser pump source, cw output powers of several mW were obtained.     

真空条件下激光诱导光纤损伤特性研究

实验研究并分析了调Q Nd:YAG 脉冲激光诱导光纤损伤特性.设计了在真空条件下全石英光纤传输1064 nm 脉冲激光实验.通过将激光注入光纤端面气压降低到10—100 Pa, 光纤端面击穿阈值提高到大气环境下的185 倍.结合光纤端面损伤形貌分析可知,光纤端面损伤主要是由于激光驻波场和烧蚀共同作用的结果,光纤端面或内部大量的缺陷降低了光纤抗激光损伤的能力.在真空条件下由于光纤端面光学击穿阈值的提高,激光诱导光纤损伤特性又表现出了另外一种损伤模式——光纤初始输入段损伤.它发生在光纤输入段附 关键词： 激光损伤 光束传输 真空 石英光纤     

Laser Performance of Neodymium Doped Phosphate Glass Fiber Pumped by a 800 nm LD

Single-mode Nd3+-doped phosphate glass fiber with a core diameter of 8 μm was prepared. Laser properties pumped by an 800 nm laser diode were measured using a Fabry-Petor cavity. Laser emission centered at the wavelength of 1.053 μm,and a 1.053 μm CW laser with output power of 8.36 mW and slope efficiency of 30.6% were observed.     

Laser Performance of Neodymium Doped Phosphate Glass Fiber Pumped by a 800 nm LD

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Acoustic attenuation of hybrid silencers

The acoustic attenuation of a single-pass, perforated concentric silencer filled with continuous strand fibers is investigated first theoretically and experimentally. The study is then extended to a specific type of hybrid silencer that consists of two single-pass perforated filling chambers combined with a Helmholtz resonator. One-dimensional analytical and three-dimensional boundary element methods (BEM) are employed for the predictions of the acoustic attenuation in the absence of mean flow. To account for the wave propagation in absorbing fiber, the complex-valued characteristic impedance and wave number are measured. The perforation impedance facing the fiber is also presented in terms of complex-valued characteristic impedance and wave number. The effects of outer chamber diameter and the fiber density are examined. Comparisons of predictions with the experiments illustrate the need for multi-dimensional analysis at higher frequencies, while the one-dimensional treatment provides a reasonable accuracy at lower frequencies, as expected. The study also shows a significant improvement in the acoustic attenuation of the silencer due to fiber absorption. Multi-dimensional BEM predictions of a hybrid silencer demonstrate that a reactive component such as a Helmholtz resonator can improve transmission loss at low frequencies and a higher duct porosity may be effective at higher frequencies.     

材料表面处理用强流电子回旋共振离子源

介绍一台2.45 GHz永磁强流电子回旋共振离子源,其外径160mm,高90 mm,放电室直径70 mm,高50 mm。微波馈入采用介质耦合方式,微波窗由一块f50 mm10 mm柱形BN和两块f30 mm10 mm的柱形陶瓷构成。离子源工作在脉冲模式下,采用三电极引出系统,最高引出电压达到100 kV,在微波输入功率300 W、进气量0.4 mL/min时,可引出峰值超过30 mA的氮离子束,在距离离子源引出孔1200 mm位置处的束流均匀区直径大于200 mm。     

基于低非线性系数光子晶体光纤的全光纤高效超连续谱光源

 报道了一种基于低非线性系数光子晶体光纤的全光纤高效率超连续谱产生系统。将光纤锁模激光器输出的脉宽5 ps、重复频率20 MHz、平均功率50 mW的脉冲,输入到15 μm的大模场光纤中进行放大,通过与两级芯径较小的短光纤模场匹配缩小输出的模场直径后,输入到20 m低非线性系数的光子晶体光纤,获得的超连续谱波长覆盖范围宽于650～1 700 nm。输入光子晶体光纤的泵浦光功率为740 mW,输出超连续光功率为670 mW,转换效率大于90%。实验研究了超连续光谱展宽的过程,从理论上进行了分析解释。