High-speed electrooptic deflector and its application to picosecondpulse generation

New types of electrooptic deflectors with high speed and high efficiency, which are useful for ultrafast optical switching and ultrashort optical pulse generation, are described. These deflectors are driven by an X-band standing wave along the microstrip line on an electrooptic crystal. A time-varying spatial slope of the refractive index is induced in the crystal by the electric standing wave. As a result, the ultrafast deflection is carried out. The operation of such deflectors constructed on a LiTaO₃ crystal using a 514.5-nm CW argon laser and a 9.35-GHz driving frequency was confirmed experimentally. In addition, the optical pulse compression from CW to 9.35 GHz, 16 ps was carried out with a diffraction grating, and picking out the 18.7-GHz, 8-ps pulse train was also carried out using a slit as a temporal window     

Nano-graphoepitaxy of semiconductors for 3D integration

The advantages of integrating semiconductor devices at more than one level (‘3D integration’) are now recognized. Key to achieving monolithic 3DICs is the ability to form single crystal semiconductor islands at the upper level without unduly heating the lower level structures. In prior work a surface relief grating of 3.8 μm pitch in the substrate was used to mediate single crystal formation while continuous wave (CW) heating a thin film of amorphous silicon; the term ‘graphoepitaxy’ was coined. CW heating is not possible in our case because it would overheat the lower layers. Moreover the area of the crystallites need only be about 100 nm to accommodate today’s transistors. Thus we have chosen a substrate grating pitch of 190 nm (hence the term ‘nano-graphoepitaxy’) and a modulated CW laser to reduce the heating time to several μs. Preliminary results indicate the substrate grating lines can indeed determine the position of the crystallite boundaries when the film thickness is 100 nm; the effect is much less pronounced in 500 nm thick films.     

All-optical generation of microwave and Millimeter wave using a two-frequency Bragg grating-based Brillouin fiber laser

A novel all-optical technique for microwave/millimeter-wave generation using two-frequency fiber Bragg grating (FBG)-based Brillouin fiber laser is presented. The mechanism for the microwave and millimeter-wave generation is theoretically analyzed. An approximately 33-GHz millimeter wave can be achieved through mixing the pump wave with the third Stokes' wave. In the experiment, an 11-GHz microwave signal is attained. The microwave frequency can be tuned by varying temperature of the fiber Fabry-Pe/spl acute/rot cavity of the Brillouin fiber laser. A more than 100-MHz tuning range around a frequency of 11 GHz is experimentally achieved.     

基于复合光栅镜的角向偏振光产生研究

为了得到角向偏振光输出,采用严格耦合波分析方法,设计了一种复合光栅镜。先通过对Ge光栅的伪博世工艺刻蚀特性的研究,得到了高深宽比的无定型Ge光栅。然后在栅槽底部引入了随机分布的Ge纳米针,在该光栅上依次镀金膜和介质保护膜,得到介质-金属复合光栅镜。最后将该复合光栅镜用作轴快流CO2激光器谐振腔尾镜,得550W角向偏振光输出。结果表明,纳米柱及金栅脊的引入使得该复合光栅镜具有很高的偏振选择性。     

Femtosecond optical pulse generation from a CW laser using anelectrooptic phase modulator featuring lens modulation

We report a novel electrooptic phase modulator featuring lens modulation and its application to the electrooptic chirping compression method for ultrashort optical pulse generation. In the pulse generation experiment, pedestal free optical pulses of 550 fs in width with a 16.25-GHz repetition rate were obtained by the group delay dispersion of a grating pair from a CW Ar laser. Furthermore, the electrooptic chirping compression method with the electrooptic phase modulator featuring lens modulation is applicable to the negative group delay dispersion as well as positive group delay dispersion     

Repetition rate, using a mode-locked hybrid distributed Braggreflector (ML-HDBR) laser source

In the present paper we report the realization of a mode-locked hybrid distributed Bragg reflector (HDBR) laser for picosecond optical pulse generation at 10-GHz repetition rate, 12.7-ps 2-mW optical pulses, with 400-MHz locking bandwidth have been obtained by using a saturated (95% of peak reflectivity) Gaussian Bragg grating. Linear phase gratings have shown even better results in terms of stability and output power (7 mW), whereas so far 15 ps of pulsewidth has been achieved, mainly limited by the spectral bandwidth of the grating. Key features of this realization are the intrinsic simplicity and the compactness of the laser source     

利用半导体可饱和吸收镜实现的全光纤被动锁模激光器

设计了包含半导体可饱和吸收镜(SESAM)、单包层高掺Yb增益光纤和光纤布拉格光栅(FBG)的全光纤激光器,实现了皮秒级,中心波长约为1064 nm,3 dB线宽约为0.4 nm,重复频率约为17.3 MHz的稳定的连续(CW)被动锁模脉冲输出。观察并分析了输出激光随抽运功率升高和降低的变化过程,升高过程中连续锁模启动时抽运功率阈值为50 mW,降低过程中能够实现稳定锁模的最小抽运功率为37 mW。随着抽运功率的加大,首先出现调Q现象。然后出现连续锁模,并伴有很小幅度的调Q现象。继续加大功率,脉冲会出现分裂;抽运功率越大,单脉冲分裂成的多脉冲越多,多脉冲调制越强。在较少脉冲演变为较多脉冲的过程中,会出现调制的不稳定性。当抽运功率足够大时.会出现多脉冲个数及峰值的不稳定现象。半导体可饱和吸收镜被动锁模会使输出激光谱线加宽,随着抽运功率的加大和锁模的加强,输出激光谱线逐渐加宽。随着脉冲分裂个数增多,单个脉冲脉宽变窄。在多脉冲调制阶段,外界微扰会对系统产生一定影响。     

Widely tunable continuous-wave InGaAsP/InP sampled grating lasers

The 1.55 μm widely tunable sampled grating lasers described here show significant improvements over those previously reported. The authors have obtained, for the first time, continuous wave (CW) operation with 62 nm CW tuning range, 30-50 dB MSR, 10 mW output power, and monotonic tuning     

Multifrequency laser with reduced intracavity wave mixing

We demonstrate a ten-channel 100-GHz spacing, waveguide grating router multifrequency laser that has significantly reduced intracavity wave mixing. The mixing products for the improved design are now too small to cause significant laser fluctuations during simultaneous multichannel operation. This was accomplished by reducing the shared waveguide length to 150 μm. We provide evidence that a significant portion of the remaining wave mixing occurs in the intracavity waveguide grating arms     

HCN激光器及亚毫米波波长的测量

简要地描述工作在亚毫米波段的连续波HCN(氰化氢)气体激光器的结构及工作特性,并分别应用反射光栅法及法布里-珀罗干涉仪法对HCN激光器的输出波长进行测量.其测量精度反射光栅法达到1%;法布里-珀罗干涉仪法达到0.1%.     

Picosecond signal sampling and multiplication by using integrated tandem light modulators

A picosecond signal sampling experiment was performed successfully by using integrated optic technologies. Two interferometric modulators of the traveling-wave and lumped types were integrated in series on a LiNbO3crystal surface. The traveling-wave modulator was oprated as a sampling gate activated by an electrical pulse train of 1-GHz repetition from a comb generator, while the lumped one was driven by a 2-GHz CW signal. The aperture time of the gate was estimated about 52 ps from the measurement using the image tube streak camera modified to sinusoidal scan at 1 GHz. Also a signal multiplication experiment was carried out using 100- and 10-MHz CW signals.     

Ultrawide AWG with hyper-Gaussian profile

We present the principle of hyper-Gaussian arrayed waveguide grating (AWG), applied successfully to realize an ultraflat 500-GHz spacing demultiplexer with 1-dB passband above 80% of the channel spacing, and a zero chromatic dispersion 50-GHz spacing wide-band AWG.     

Multiple-phase shift super structure grating DBR lasers for broadwavelength tuning

Broad range wavelength tuning in distributed Bragg reflector (DBR) lasers using a super structure grating with multiple phase shifts is discussed. Experimental results indicate that the laser achieves a maximum tuning range of 105 nm with stable single-mode continuous wave (CW) operation     

Millimeter Wave Radar for detecting the speech signal applications

MilliMeter Wave (MMW) Doppler Radar with grating structures for the applications of detecting speech signals has been discovered in our laboratory. The operating principle of detection the acoustic wave signals based on the Wave Propagation Theory and Wave Equations of The ElectroMagnetic Wave (EMW) and Acoustic Wave (AW) propagating, scattering, reflecting and interacting has been investigated. The experimental and observation results have been provided to verify that MMW CW 40GHz dielectric integrated radar can detect and identify out exactly the existential speech signals in free space from a person speaking. The received sound signal have been reproduced by the DSP and the reproducer.     

光纤布喇格光栅动态响应特性的计算和分析

利用传输矩阵法和龙格-库塔法分析光纤布喇格光栅的反射谱和时延特性,无法得到输入信号变化时光栅的动态响应。为了计算光纤光栅的动态响应,利用坐标变换结合有限差分法求解耦合波方程,在此基础上计算了光纤布喇格光栅在连续波与高斯脉冲输入的动态响应特性,并与龙格-库塔法比较,结果证明了此算法的正确性。可以利用本文中提出的方法分析输入信号在光纤光栅中的动态传输特性。     

一种新颖的毫米波集成功率合成器

本文介绍一种结构新颖的毫米波Ｅ面混合集成功率合成器及其设计方法。功率合成器电路由鳍线和Ｅ面线构成,输出端口为标准矩形波导。具有结构紧凑、调试简便的优点。采用两耿氏管,在Ｋａ波段,６３０ＭＨｚ的机械调谐带宽内连续波输出功率大于２００ｍＷ,最大输出功率为２９３ｍＷ。     

40-mW 650-nm distributed feedback lasers

Using a buried second-order grating in a single-mode GaInP-AlInP laser structure, we obtain single-spatial- and longitudinal-mode operation at 652 nm. Over 40-mW continuous wave (CW) is obtained at room temperature (RT), with efficiencies and far fields comparable to conventional Fabry-Perot lasers. The devices are continuously tunable with current and temperature and exhibit no mode hops, and thus should be useful for applications where short wavelength and longitudinal mode stability is required, such as spectroscopy, interferometry, or optical storage     

空间探测光栅光谱仪新进展

空间探测光栅光谱仪是指利用光栅作为主色散元件在卫星轨道上对目标探测的光谱仪。阐述了用于空间探测的光栅光谱仪国内外最新发展状况,根据最新的空间探测光栅光谱仪的结构和技术指标,分析了空间光栅光谱仪的应用范围和发展方向。应用范围主要是空间环境探测和对地观测。其中空间环境主要关注电离层、臭氧层和温室气体的总量及廓线,对地观测主要是获得图谱合一的地球表面参数,在得到二维图像信息的同时,增加了一维光谱信息,使得信息量大大增加。最新的发展方向是探测谱段向紫外和红外延伸,系统覆盖更大的视场角,空间分辨率逐步提高。结合光谱仪系统可靠性高的优点,空间光栅光谱仪非常适于空间和地面环境的探测。     

Magnetostatic surface waves in a ferrite/dielectric/metal-strip-grating structure

The dispersion relation for magnetostatic surface waves in a ferrite/dielectric/metal-strip-grating structure is obtained. It is shown that dispersion of magnetostatic surface waves must be qualitatively the same as in a ferrite/dielectric/metal structure, while the slope of the dispersion curve in the region of backward magnetostatic waves existing in a ferrite/dielectric/grating structure (and in a ferrite/grating structure in particular) is considerably higher than the slope of this curve corresponding to a ferrite/dielectric/metal structure. It is found that this phenomenon can be explained by the dependence of the grating’s shielding capability on the wave number of magnetostatic surface waves. A grating shielding parameter is introduced and dependences of this parameter on the wave number that can be used to explain the phenomena observed in the experiment are determined.     

S波段连续波输出功率20W的SiC MESFET

采用自主开发的SiC外延材料和工艺技术,相继实现了S波段连续波状态下输出功率瓦级和10 W的SiC MESFET。经过版图设计的改进和工艺条件的优化,取得了S波段连续波状态下输出功率大于20 W,功率增益大于12 dB,功率附加效率大于30%的SiC MESFET研制结果。器件的功率增益和输出功率较以往的研制结果均得到显著提高,器件的反向截止泄漏电流也大幅度降低。由于器件未采用内匹配结构,其体积也比一般内匹配器件的体积小。研制结果为多胞合成实现更大功率输出的器件创造了条件,也使S波段连续波大功率输出器件的研制水平上了一个新的台阶。