Phase locking of fibre lasers by self-imaging resonator

Experimental demonstrations of the use of a self-imaging resonator in the phase locking of two fibre lasers are presented. The output power of the phase-locked fibre laser array exceeded 2 W Successful attempts of phase locking show that the fibre laser array is not only capable of producing high Output Power but also large on-axis intensity by this method.

On-Chip All-Optical Passive 3.55 Gbit/s NRZ-to-PRZ Format Conversion Using a High-Q Silicon-Based Microring Resonator

We report the experimental result of all-optical passive 3.55 Gbit/s non-return-to-zero (NRZ) to pseudo-return-to-zero (PRZ) format conversion using a high-quality-factor (Q-factor) silicon-based microring resonator notch filter on chip. The silicon-based microring resonator has 23800 Q-factor and 22 dB extinction ratio (ER), and the PRZ signals has about 108 ps width and 4.98 dB ER.

Analysis of directional emission in square resonator lasers with an output waveguide

Square microcavity laser with an output waveguide is proposed and analyzed by the finite-difference time-domain (FDTD) technique. For a square resonator with refractive index of 3.2, side length of 4 microns, and output waveguide of 0.4-micron width, we have got the quality factors (Q factors) of 6.7×10~2 and 7.3×10~3 for the fundamental and first-order transverse magnetic (TM) mode near the wavelength of 1.5 microns, respectively. The simulated intensity distribution for the first-order TM mode shows that the coupling efficiency in the waveguide reaches 53%. The numerical simulation shows that the first-order transverse modes have fairly high Q factor and high coupling efficiency to the output waveguide. Therefore the square resonator with an output waveguide is a promising candidate to realize single-mode directional emission microcavity lasers.

Potential light source for photonic integrated circuits based on the equilateral triangle resonator

The semiconductor microlasers based on the equilateral triangle resonator (ETR) can be fabricated from the edge-emitting laser wafer by dry-etching technique, and the directional emission can be obtained by connecting an output waveguide to one of the vertices of the ETR. We investigate the mode characteristics, especially the mode quality factor, for the ETR with imperfect vertices, which is inevitable in the real technique process. The numerical simulations show that the confined modes can still have a high quality factor in the ETR with imperfect vertices. We can expect that the microlasers is a suitable light source for photonic integrated circuits.

Eigenmode confinement in semiconductor microcavity lasers with an equilateral triangle resonator

We analyze the mode behaviors for semiconductor lasers with an equilateral triangle resonator by deriving the mode field distribution and the eigenvalue equation. The eigenvalue equation shows that the longitudinal mode wavelength interval is equivalent to that of a Fabry-Perot cavity with the cavity length of 1.5a, where a is the side length of the equilateral triangle resonator. The transverse waveguiding is equivalent to as a strip waveguide with the width of root 3a/ 2, and the number of transverse modes supported by the resonator is limited by the total reflection condition on the sides of the equilateral triangle. Semiconductor microcavity laser with an equilateral triangle resonator is suitable to realize single mode operation, and the mode wavelength can be adjusted by changing the side length.

双面二维硅微条探测器的沾污失效分析及修复；Contamination failure analysis and repairing for double side two dimensional silicon microstrip detectors

硅微条探测器通过微电子工艺制作,易因沾污导致性能下降甚至失效;裸露的键合引线,也易因机械力形成隐性或显性失效。对上述现象的研究可用于修复、维护探测器并在设计和工艺流程中改进其性能。本文通过光学、电气手段分析其结构和制作工艺流程,根据沾污性质在不同条件下清洗探测器,中测后根据芯片图形、封装方式和电气要求修复探测器,最后采用同位素α能谱测试修复效果。对一块沾污后失效(无法加载偏压)的硅微条清洗后在大气环境,N面接地,P面加载负偏压条件下进行了测试,结果显示:170 V全耗尽,平均漏电流2.94μA,5.486 MeV的α峰能量分辨率约1.28%。失效键合所在条的另一面各条能谱观测到假峰,键合修复后消除。因沾污失效的硅微条探测器经过合适的清洗、修复,部分可以恢复性能,但清洗对表面和结构有损伤,须谨慎。另外,键合失效后,因信号不能引出导致的电荷积累会通过电容效应影响其它灵敏区。文章提示,探测器应存放于洁净,恒温,低湿度,避光,避强电磁干扰的环境,以提高能量和位置分辨率,并增加工作稳定性,延长使用寿命。

Coupling of seagrass (Cymodocea nodosa) patch dynamics to subaqueous dune migratio

The coupling between patch dynamics - described by the patch growth (horizontal and vertical), patch mortality, and life-history of Cymodocea nodosa (Ucria) Aschers., and the disturbance caused by the migration of subaqueous dunes over the plants was examined in a shallow NW Mediterranean bay (Alfacs Bay) where this species maintains a patchy cover. C. nodosa shoots survived substantial burial rates (up to 2.4 mm/day) by growing vertically at rates proportional to, albeit four-fold slower than, burial rates. Patch death was caused by erosion as large subaqueous dunes migrated pass the plant patch. Patch growth was fastest over the progressing slope of the dunes ( similar to 2.5 m year super(-1)) and flowering was also stimulated by sand accretion. The time interval between the passage of consecutive dunes, which sets the time window available for patch development, ranged between 2 and 6 years. This time interval allowed C. nodosa to recolonize bare substrata, with patch formation occurring about half a year after the disturbance, and also allowed established shoots to complete their life-cycle and produce seeds and thus enable subsequent recolonization. The time windows available for patch development also set an upper limit to patch size of about 26 m. Significant cross correlations between dune topography and patch dynamics and plant flowering frequency provide evidence that the spatial heterogeneity in the vegetation is closely associated with the disturbance imposed by the migration of sand dunes. The migration of subaqueous dunes maintains C. nodosa in a continuous state of colonization involving spatially asynchronous patch growth and subsequent mortality, which is ultimately responsible for the characteristic patchy landscape of this Bay. 

A mica-modified quartz resonator for a quartz crystal microbalance study

Mica, as a bridge of the study for combining between quartz crystal microbalance (QCM) and atomic force microscope (AFM), was successfully modified onto the piezoelectric quartz crystal (PQC). This mica-modified piezoelectric quartz crystal (mica-PQC) can be stably oscillated with a shift frequency of +/-1 Hz per half an hour in air. Using this mica-PQC, the processes of DNA adsorbed onto the mica surface were studied in liquid phase. The results show that a bivalent cation, such as Mn2+, can be used as an ionic bridge to immobilize DNA on mica surface. The image of DNA on the mica surface was also obtained by AFM. Mica-PQC gives the possibility of a combination between QCM and AFM in situ.

Experimental investigation of an unstable ring resonator with 90-deg beam rotation for a chemical oxygen iodine laser

We report the experimental results of an unstable ring resonator with 90-deg beam rotation for a kilowatt class chemical oxygen iodine laser (COIL). The distributions of near-field phase and far-field intensity were measured. A beam quality of 1.6 was achieved when the COIL average output power was approximately 5 kW. (C) 1999 Optical Society of America.

Vortex dynamics in the studies of looping in tropical cyclone tracks

This paper proposes criteria for predicting the tendency of looping in tropical cyclone tracks using the approach of vortex dynamics. We model the asymmetric structure of a cyclone by a system of vortex patches. The evolution of such system of vortices is simulated by the method of contour dynamics. A new set of exact analytic formulas for contour dynamics calculations is derived, which is shown to be more computationally effective. Based on point-vortex models, we derive analytic formulas for the criteria of looping in a cyclone track. From numerical experiments, the simulated trajectories obtained from the point-vortex system and vortex patch system agree quite well. Hence, the looping criteria obtained from the point-vortex system can be applied by forecasters to stay alert for tendency of looping in a cyclone track. To demonstrate the applicability of the proposed criteria, the trajectory of Typhoon Yancy (9012), whose field data are available from ''TCM-90'', is simulated. The case study shows that the asymmetric structure similar to the pattern of a beta gyre is responsible for its recurvature when Yancy landed Fujian Province, China on 20 August 1990.

Near-diffraction-limited, 35.4 W laser-diode end-pumped Nd:YVO4 slab laser operating at 1342 nm

A diode stack end-pumped Nd:YVO4 slab laser at 1342 nm with near-diffraction-limited beam quality by using a hybrid resonator was presented. At a pump power of 139.5 W, laser power of 35.4 W was obtained with a conversion efficiency of 25.4% of the laser diode to laser output. The beam quality M-2 factors were measured to be 1.2 in the unstable direction and 1.3 in the stable direction at the output power of 29 W. (C) 2009 Optical Society of America

溶胶-凝胶光波导环形谐振腔的挥发性有机化合物传感特性

采用溶胶-凝胶法制作波导环形谐振腔, 讨论了环形谐振腔器件的传输特性。测量了在不同物质、不同体积分数的挥发性有机化合物(VOC)蒸气气氛下器件的传输光谱的敏感性。结果表明, 谐振波长随甲醇、乙醇、丙醇等醇类化合物, 以及丙酮、甲醛等蒸气体积分数的上升而向长波方向移动, 具有高的灵敏度, 且两者基本呈线性关系。其中, 对丙醇最敏感, 灵敏度达到1.403 pm/10-6。对甲烷和二甲苯也有微弱反应, 但是其灵敏度很低。也测量了水蒸气对传输谱特性的影响。观察到传输谱衬比度对不同挥发性有机化合物物质蒸气的不同敏

一种新型结构的单纵模光纤激光器

单纵模掺铒光纤激光器在光通信和光传感等方面有着广泛的应用前景。设计了一种新型的光纤激光器，在光纤环形镜中嵌入未抽运的掺铒光纤作为可饱和吸收体以抑制多纵模，用光纤环谐振腔作为滤波器抑制拍频噪声，用光纤光栅作为波长选择器件，最终得到了单纵模输出并消除了拍频噪声。使用零拍法测量其线宽小于频谱仪的低频极限5kHz。实验结果证明了可饱和吸收体和光纤环的功能。

Characteristics of an add-drop filter composed of a Mach-Zehnder interferometer and double ring resonators

A planar lightwave circuit (PLC) add-drop filter is proposed and analyzed, which consists of a symmetric Mach-Zehnder interferometer (MZI) combined with double microring resonators. A critical coupling condition is derived for a better box-like drop spectrum. Comparisons of its characteristics with other schemes, such as a MZI with a single ring resonator, arepresented, and some of the issues about device design and fabrication are also discussed.