The Fluid Phenomena In the Crystallization Of the Protein Crystal

This paper reports that an optical diagnostic system consisting of Mach-Zehnder interferometer with a phase shift device and image processor has been used for study of the kinetics of protein crystal growing process. The crystallization process of protein crystal by vapour diffusion is investigated. The interference fringes are observed in real time. The present experiment demonstrates that the diffusion and the sedimentation influence the crystallization of protein crystal which grows in solution, and the concentration capillary convection associated with surface tension occurs at the vicinity of free surface of the protein mother liquor, and directly affects on the outcome of protein crystallization. So far the detailed analysis and the important role of the fluid phenomena in protein crystallization have been discussed a little in both space- and ground-based crystal growth experiments. It is also found that these fluid phenomena affect the outcome of protein crystallization, regular growth, and crystal quality. This may explain the fact that many results of space-based investigation do not show overall improvement.

利用x射线激光干涉诊断等离子体电子密度

x射线激光探针干涉方法是诊断高温高密度激光等离子体电子密度等信息的重要工具．利用神光Ⅱ装置输出激光驱动的类镍-银x射线激光作为探针，成功地进行了马赫-曾德尔干涉法诊断实验，获得了清晰的包含等离子体信息的动态干涉条纹图像，并据此给出了待测C8H8等离子体临界面附近电子密度的空间分布。

基于3×3耦合器的马赫-曾德尔干涉仪的光纤光栅波长解调技术

介绍了一种基于3×3和2×2光纤耦合器构成的非平衡马赫-曾德尔干涉仪的波长解调方案。理论分析和数据对比表明，相对于由两个2×2光纤耦合器构成的马赫-曾德尔干涉仪，本干涉仪具有宽谱的灵敏度、能跟踪波长的变化方向和相位展开的优点，实验方案用于测量固定在悬臂梁上的传感光纤布拉格光栅（FBG）的峰值波长变化，获得了±1pm的静态波长解调精度，在10Hz处的动态分辨率为27nε/√Hz。相位展开算法使得应变测量范围达到了2014με，对应的相位变化为3．22π。

利用数字全息干涉术观察RuO2：LiNbO3晶体中畴反转的区域特性

利用马赫-曾德尔干涉光路和V光学透镜系统，以部分畴反转的掺钌铌酸锂晶体（RuO2：LiNbO3）的透射光作为物光来记录全息图，并在数值再现过程对其进行频域滤波以实现物场波前信息的数值重建，检测出在一定电压作用下晶体内部折射率变化的二维分布．检测结果证实;晶体中发生畴反转的区域与发生电色效应的区域严格相符．数字全息干涉术非接触、无干扰、无破坏的优势在准实时监控、检测和分析铌酸锂晶体畴反转方面有很好的应用前景．

利用脉冲重复率倍增和时域泰伯效应实现毫米波脉冲的产生

我们提出了一种新颖的利用脉冲重复率倍增和时域泰伯效应实现毫米波脉冲信号产生的光学方法。在我们的方案中，一个级联的马赫振德干涉仪被用来实现脉冲重复率倍增，一个线性的啁啾光纤光栅被用来实现时域泰伯效应。文中对这种方法的基本理论进行了分析，并给出了相应的数值模拟的结果。研究结果显示这种灵活的毫米波脉冲信号产生的方案在未来的宽带的Radio over Fiber技术将有一个很好的潜在的应用。

Interaction between the intrinsic second- and third-order optical fields in an Al0.53Ga0.47N/GaN heterostructure

We present an experimental demonstration of the interaction between the intrinsic second- and third-order optical fields in an Al0.53Ga0.47N/GaN heterostructure. The sample was deposited by metal-organic chemical vapor deposition on (0001) sapphire. The nonlinear optical coefficients of the sample, which were measured with a Mach-Zehnder interferometer system, quadratically increase with the applied modulating voltage, indicating the existence of the third-order optical field. The third-order signal was then detected by the Z-scan method and we calculated the built-in dc field on the AlGaN/GaN interface to confirm the strong interaction between the intrinsic second- and third-order optical fields. (c) 2008 American Institute of Physics.

High-speed 2 x 2 silicon-based electro-optic switch with nanosecond switch time

A 2 x 2 electro-optic switch is experimentally demonstrated using the optical structure of a Mach-Zehnder interferometer (MZI) based on a submicron rib waveguide and the electrical structure of a PIN diode on silicon-on-insulator (SOI). The switch behaviour is achieved through the plasma dispersion effect of silicon. The device has a modulation arm of I mm in length and cross-section of 400 nmx340 nm. The measurement results show that the switch has a V pi L pi figure of merit of 0.145 V-cm and the extinction ratios of two output ports and cross talk are 40 dB, 28 dB and -28 dB, respectively. A 3 dB modulation bandwidth of 90 MHz and a switch time of 6.8 ns for the rise edge and 2.7 ns for the fall edge are also demonstrated.

New type of multimode-interference-type thermo-optic variable optical attenuator

A thermo-optic variable optical attenuator (VOA) based on a Mach-Zehnder interferometer and multimode-interference coupler is fabricated. Not a single-mode but a multimode waveguide is used as the input and output structures of the optical field, which greatly reduces the coupling loss of the VOA with a normal single-mode fiber. The insertion loss of the fabricated VOA is 2.52 to 2.82 dB at the wavelength of 1520 to 1570 nm. The polarization dependent loss is 0.28 to 0.45 dB at the same wavelength range. Its maximum attenuation range is up to 26.3 dB when its power consumption is 369 mW. The response frequency of the fabricated VOA is about 10 kHz. (C) 2004 Society of Photo-Optical Instrumentation Engineers.

High speed 2x2 optical switch in silicon-on-insulator based on plasma dispersion effect

Based on free carrier plasma dispersion effect, a 2 x 2 optical switch is fabricated in a silicon-on-insulator substrate by inductively coupled-plasma technology and ion implantation. The device has a Mach-Zehnder interferometer structure, in which two directional couplers serve as the power splitter and combiner. The switch presents an insertion loss of 3.04 dB and a response time of 496 ns.

Rearrangeable nonblocking thermo-optic 4 x 4 switching matrix in silicon-on-insulator

A rearrangeable nonblocking thermo-optic 4 x 4 switching matrix is demonstrated. The matrix, which consists of five 2 x 2 multimode interference-based Mach-Zehnder interferometer (MMI-MZI) switch elements, is fabricated in silicon-on-insulator waveguide system. The average excess loss for the optical path experiencing 2 and 3 switch elements is 6.6 and 10.1 dB respectively. The crosstalk in the matrix is measured to be between -12 and -19 dB. The switching time of the device is less than 30 mu s.

SOI-based 16x16 thermo-optic waveguide switch matrix

A 16 x 16 thermo-optic wavelenght switch matrix has been designed and febricated on silicon-on-insulator wafer. For reducing device lenght, blocking switch matrix configuration is chosen. The building block of a matix is a 2 x 2 cell with Mach-Zehnder interferometer configuration, where a multi-mode interferometer serves as splitters/combiners. Spot size converters and isolating grooves are integrated on the same chip to reduce loss and power consumption. Average power consumption of the switch cell is 220 mW. The switching time of a switch cell is less than 3 mu s.

A 2x2 optical switch based on plasma dispersion effect in silicon-on-insulator

Based on Mach-Zehnder interferometer (MZI) structure, a 2 x 2 optical switch is fabricated on SOI wafer. Modulation of the refractive index of MZI arms is achieved through free carriers plasma dispersion effect of silicon. The device presents an insertion loss as low as 3.44 dB and a response time as small as 300 ns. The crosstalk and extinction ratio are -15.54 and 14.9 dB, respectively. Detailed analysis and explanation of the operating behaviors are also presented. (C) 2005 Elsevier B.V. All rights reserved.

Improved optical heterodyne methods for measuring. frequency responses of photodetectors

An improved optical self-heterodyne method utilizing a distributed Bragg reflector (DBR) tunable laser and an optical fiber ring interferometer is presented in this paper. The interference efficiency can be increased by 7 dB compared with the scheme using the conventional Mach-Zehnder interferometer. The unsteady process that the beating frequency experiences in each tuning period is investigated. According to the measurement results, the wavelength and optical power of the tunable laser will be steady when the square-wave frequency is lower than 300 kHz. It has been shown that when a square-wave voltage is applied to the phase section of the tunable laser, the laser linewidths vary in a wide range, and are much larger than that under dc voltage tuning. The errors caused by the variations in the linewidth of the beat signal and optical power can be eliminated using the proposed calibration procedures, and the measurement accuracy can, therefore, be significantly improved. Experiments show that the frequency responses obtained using our method agree well with the data provided by the manufacturer, and the improved optical self-heterodyne method is as accurate as the intensity noise technique.

Pockels effect in GaN/Al-x,Gal(1-x)N superlattice with different quantum structures - art. no. 69841G

The linear electro-optic (Pockels) effect of wurtzite gallium nitride (GaN) films and six-period GaN/AlxGa1-xN superlattices with different quantum structures were demonstrated by a polarization-maintaining fiber-optical Mach-Zehnder interferometer system with an incident light wavelength of 1.55 mu m. The samples were prepared on (0001) sapphire substrate by low-temperature metalorganic chemical vapor deposition (MOCVD). The measured coefficients of the GaN/AlxGa1-xN superlattices are much larger than those of bulk material. Taking advantage of the strong field localization due to resonances, GaN/AlxGa1-xN SL can be proposed to engineer the nonlinear responses.

High speed silicon optical switches based on carrier depletion - art. no. 67812D

The novel design of a silicon optical switch on the mechanism of a reverse p-n junction is proposed. The figuration of contact regions at slab waveguides and the ion implantation technology for creation of junctions are employed in the new design. The two-layer rib structure is helpful for reduction of optical absorption losses induced by metal and heavily-doped contact. And more, simulation results show that the index modulation efficiency of Mach-Zehnder interferometer enhances as the concentrations of dopants in junctions increase, while the trade-off of absorption loss is less than 3 dB/mu m. The phase shift reaches about 5 x 10(-4) pi/mu m at a reverse bias of 10V with the response time of about 0.2ns. The preliminary experimental results are presented. The frequency bandwidth of modulation operation can arrive in the range of GHz. However, heavily-doped contacts have an important effect on pulse response of these switches. While the contact region is not heavily-doped, that means metal electrodes have schottky contacts with p-n junctions, the operation bandwidth of the switch is limited to about 1GHz. For faster response, the heavily-doped contacts must be considered in the design.