硅基底平面波导光通讯集成器件的模拟、设计及工艺

随着平面波导制作工艺的日益成熟 ,制造精度的不断提高 ,成本的持续下降 ,平面波导光集成器件尤其是 Si基底上 Si O2 平面波导集成器件在光通信系统中的应用更加重要和广泛 .Y分支分束器、MMI耦合器、阵列波导光栅 (AWG)和蚀刻衍射光栅 (EDG)等平面波导集成器件正扮演着越来越重要的作用 ,BPM等数值计算方法在这些器件的设计和模拟中也起了重要作用 .本文就此作了一些探讨 .     

Variable optical delay line with diffraction-limited autoalignment

We demonstrate a novel type of variable, optical delay line that ensures diffraction-limited parallelism and collinearity in the delayed beam and is independent of the mechanical quality of the translation stage.     

Two-sided through-wafer interconnect for optical spiral delay line

True-time-delay devices could significantly contribute to improving the performance of many optical systems in applications such as sensing, ranging, communication and signal processing. Delay devices based on spiral optical waveguides are of special interest due to their small size and relatively low power attenuation. In this paper, we propose to fabricate spirals on both sides of a wafer, where the coupling between them is through a vertical interconnect. The novel through-wafer interconnect has a level of attenuation that compares competitively with that obtained with a conventional s-shaped interconnect between two interleaved spirals and considerably simplifies the waveguide design and fabrication.     

Dispersion in a grating-based optical delay line for optical coherence tomography

Optical coherence tomography (OCT) is a high-resolution imaging technology based on low-coherence interferometry. When OCT imaging is performed in biological tissue, dispersion almost inevitably occurs. We quantify the group-velocity dispersion that a grating-based optical delay line may induce and its contribution to the axial point-spread function of OCT. Among the practical reasons for modeling the dispersion in grating-based optical delay line is that, at maximum compensation, it can provide insight into the dispersive properties of tissues.     

采用频域快速延迟线的光学相干层析系统的研制

建立了一套单模光纤型光学相干层析(OCT)成像系统。系统采用了不同于国内其他组的新型频域快速扫描延迟线(FD-ODL)和外差平衡接受技术,采取了一系列提高系统信噪比的方法,成功地实现高信噪比(113dB)、高分辨率、大成像深度的层析图像的提取,获得了纵向分辨率9μm、横向分辨率10μm、深度2.88μm的清晰的皮肤OCT图像。该系统比传统的采用时域延迟线的OCT在信噪比上高出了一个量级。     

Kilohertz scanning optical delay line employing a prism array

A kilohertz scanning optical delay line is demonstrated by means of employing a prism array formed by identical wedge prisms. The wedge prisms are lined up with one another and uniformly disposed on a rotational wheel. The optical path length of a light beam can thus be scanned as the prisms pass through the beam periodically. Scanning rate of 2 kHz, scanning amplitude of 3.5 mm, linearity of 99%, and duty cycle of 95% can be achieved simultaneously. Simplicity and rigidity are embedded in the design. Preliminary test results are presented.     

Double-pass rotary mirror array for fast scanning optical delay line

We have developed a fast scanning optical delay line based on a rotary mirror array. A double-pass configuration is adopted to optimize the fiber-optical coupling and thus minimize the amplitude modulation in the reflected light. The achieved scanning range is extended to over 3 mm. An additional Michelson interferometer is incorporated into the reference arm to achieve high delay repeatability. Such a device is ideal for real-time optical coherence tomography, optical Doppler tomography, and spectroscopic optical coherence tomography.     

Adsorption of Cr(VI) using silica-based adsorbent prepared by radiation-induced grafting

Silica-based adsorbent was prepared by radiation-induced grafting of dimethylaminoethyl methacrylate (DMAEMA) onto the silanized silica followed by a protonation process. The FTIR spectra and XPS analysis proved that DMAEMA was grafted successfully onto the silica surface. The resultant adsorbent manifested a high ion exchange capacity (IEC) of ca. 1.30 mmol/g and the Cr(VI) adsorption behavior of the adsorbent was further investigated, revealing the recovery of Cr(VI) increased with the adsorbent feed and the equilibrium adsorption could be achieved within 40 min. The adsorption capacity, strongly depended on the pH of the solution, reached a maximum Cr(VI) uptake (ca. 68 mg/g) as the pH was in the range of 2.5–5.0. Furthermore, even in strong acidic (4.0 mol/L HNO₃) or alkaline media (pH 11.0), the adsorbent had a sound Cr(VI) uptake capacity (ca. 22 and 30 mg/g, respectively), and the adsorption followed Langmuir mode. The results indicated that this adsorbent, prepared via a convenient approach, is applicable for removing heavy-metal-ion pollutants (e.g. Cr(VI)) from waste waters.     

A new magnetostatic wave delay line using YIG film

We have proposed a delay line of microstrip type consisting of a microstrip line fabricated on a composite substrate of two yttrium iron garnet films separated by a gadolinium gallium garnet layer. The dispersion relations are derived assuming magnetic walls at the edges of the strip. Experiments are carried out at S band with nonuniform magnetic field. Insertion loss less than 25 dB with large delay time more than 800 ns is observed experimentally. The experimental results on delay line characteristics are briefly discussed with theory     

Precise measurement of SAW velocity using SAW delay line

A method of nondestructive evaluation (NDE) by measuring the acoustic properties of materials using a surface-acoustic-wave (SAW) delay line is presented. A SAW delay line with three interdigital transducers (IDTs) deposited on a piezoelectric substrate is used to measure the SAW velocity of the sample material, using a fluid couplant. The SAW velocity is obtained from the frequency dependence of the delay line, and movement in the z-direction is not required. Measurements have been made for an anisotropic material at frequencies from 35 to 55 MHz. The experimental results agree well with the theoretical results. Moreover, it has been found that the focused SAW excited from a Fresnel-phase-plate IDT is suitable for mapping the two-dimensional variation of SAW velocity on an anisotropic sample surface.     

Programmable ultrashort optical pulse delay using an acousto-optic deflector

We present an optical pulse delay (OPD) for delaying ultrashort optical pulses that uses an acousto-optic deflector as an active component. The OPD is designed to correct for chromatic dispersion caused by the significant color spectrum of ultrashort pulses. It is intended to be used as one of the components in a three-dimensional memory system based on pulse-collision addressing in two-photon materials. Calculations show that the OPD should be able to provide 65 arbitrary delays with a random access time of ? 1 μs for 100-fs pulses. The power efficiency of the OPD can be as high as 85% and hence permits two units to be cascaded to provide more than 4000 distinct delays. The number of delays and the access time can be optimized such that a fewer number of delays are obtained with a shorter access time, which favors high-speed operations. We provide experimental results that use a Michelson interferometer to measure three different delays, approximately 1 mm apart (equivalent to ?3-ps time delay), obtained with 130-fs pulses. In addition we include an analysis of the performance of acousto-optic devices for both monochromatic light and ultrashort pulsed lasers. Finally, we provide the design of the optical pulse-delay system for a three-dimensional memory application.     

Dispersion control with a Fourier-domain optical delay line in a fiber-optic imaging interferometer

Recently, Fourier-domain (FD) optical delay lines (ODLs) were introduced for high-speed scanning and dispersion compensation in imaging interferometry. We investigate the effect of first- and second-order dispersion on the photocurrent signal associated with an optical coherence imaging system implemented with a single-mode fiber, a superluminescent diode centered at 950 nm +/- 35 nm, a FD ODL, a mirror, and a layered LiTAO3 that has suitable dispersion characteristics to model a skin specimen. We present a practical and useful method to minimize the effect of dispersion through the interferometer and the specimen combined, as well as to quantify the results using two general metrics for resolution. Theoretical and associated experimental results show that, under the optimum solution, the maximum broadening of the point-spread function through a 1-mm-deep specimen is limited to 57% of its original rms width value (i.e., 8.1 microm optimal, 12.7 microm at maximum broadening) compared with approximately 110% when compensation is performed without the specimen taken into account.     

Fast-Fourier-domain delay line for in vivo optical coherence tomography with a polygonal scanner

We demonstrate in vivo optical coherence tomography using a Fourier-domain optical delay line constructed with a commercially available polygonal scanner. The 20-faceted polygonal mirror array, capable of scanning at rates up to 15 kHz, is implemented at 4 kHz to acquire 500 x 500 pixel images at 8 frames/s with a signal-to-noise ratio of 80 dB. Features of this delay line include scalability to high repetition rates, 98.6% linearity in group delay over 2 mm, and bandwidth support exceeding 150 nm. Images are obtained in an animal model (Xenopus laevis), and limitations due to phase-delay nonlinearity and polygon asymmetry are discussed.     

Delay and dispersion characteristics of a frequency-domain optical delay line for scanning interferometry

The reflective frequency-domain optical delay line employing a diffraction grating, a lens, and a tiltable mirror has emerged as a device particularly suitable for interferometry and optical coherence tomography. The device is comprehensively described, both theoretically and experimentally, in the context of interferometry. The variations of phase and group delay produced by the device as well as its dispersive properties are described and demonstrated experimentally.     

Slot-electrode optical modulator using KTiOPO(4)

A slot-electrode optical modulator is introduced and demonstrated with KTP at 532 nm. A switching voltage of 45 V, risetime of 3.5 ns, and power capability of more than 7 Ware measured. DC modulation without application of DC voltage is discussed. Further optimization can reduce the switching voltage to 18 V.     

Device optimization of CO2 gas sensor using planar technology

A planar type Li+ ion based potentiometric CO2 micro gas sensor of size 2 x 3 mm has been fabricated on alumina substrate by combining thin and thick film technology. The heater, electrodes and electrolyte were deposited by thin film deposition technique and the sensing and reference electrodes were printed by silk screen printing technology. The optimal thickness and sintering temperature of electrolyte are 1.2 microm and 775 degrees C. The sensor with Li2CO3 and 20 mol% BaCO3 not only exhibits a good Nernstian behavior but also consistent results over a long time at 450 degrees C in dry as well as 70% RH humidity condition between 160-5000 ppm CO2 concentrations. The spreading effect of the sensing and reference materials was controlled by the addition of Al2O3:B2O3 (1:2 mol%) glass.     

恒星干涉仪延迟线系统地面随机振动响应分析

研究地面随机微振动对恒星干涉仪关键部件-光学延迟线系统性能的影响。利用美国蓝氏(Lansmont)集团生产的SAVER 3X型三轴振动仪实测地面随机振动信号,以输出的G加速度功率谱密度为激励,运用Workbench有限元分析软件计算该结构系统的随机振动响应;根据抛物镜面节点数据拟合出抛物镜面的Zernike多项式系数、抛物镜刚体平移量和抛物镜面PV和RMS值;将Zernike多项式系数导入光学系统中分析光学延迟线系统光学性能;最后利用ELCOWAT 3000电子自准直仪测量抛物镜刚体平移量,分析实际测量结果和计算理论结果偏差。分析计算结果与实验数据最大偏差7.6%,计算抛物镜面形RMS值为9.6 nm,PV值为46.1 nm,波前差为0.043λ。目前的光学延迟线的地面振动满足光学延迟线系统的稳定性要求。使用动态光学性能标准分析判断微振动对系统光学性能的影响程度,为恒星干涉仪其他子系统优化设计和隔振补偿措施提供参考。     

A position sensitive microchannelplate detector using a delay line readout anode

A new method for a two-dimensional position encoding system with microchannelplates (MCPs) involving a delay line readout anode is described. The resolution of the time measurement is 500 ps corresponding to a position resolution of 0.25 mm.     

Minimization of geometric-beam broadening in a grating-based time-domain delay line for optical coherence tomography application

This paper discusses a dispersion effect in a grating-based time-domain delay line that is different from the second- or higher-order dispersion in a grating-based Fourier-domain delay line. When the lateral broadening of the beam profile after grating dispersion exceeds the collection aperture of the reference fiber, the peripheral spectrum is decoupled by the fiber. The loss of reference spectral bandwidth by this geometric-beam broadening thus degrades the axial resolution. The polarizing-beam reflector used in the Fourier-domain delay line for suppression of lateral beam walk-off is implemented in this grating-based time-domain delay line to minimize geometric-beam broadening. Theoretical analysis and experiments are given to validate the axial resolution improvement after geometric-beam broadening is minimized. In vitro and in vivo imaging results are presented to demonstrate the improvement. It is also shown that geometric-beam broadening may exist in other optical coherence tomography reference arm configurations.