Planar and Channel Optical Waveguide Loss Measurement Using Optical Phase Conjugation in BaTiO 3

A new methodology of the propagation loss coefficient measurement with an accuracy of at least 10 -3 cm -1 is demonstrated using a single-pass transmission measurement method and beam coupling based on a self-pumped phase conjugation process in a single BaTiO 3 crystal. A new, high-precision optical "bridge system" for routine measurement of the planar waveguide propagation loss coefficient is designed.     

一种离子交换制备的玻璃光波导谐振腔滤波器

采用AgNO3、KNO3混和熔盐作为离子交换源,在K9玻璃上制备了跑道形谐振腔滤波器。测试得到该滤波器的自由光谱范围为0.178 nm,两个输出端口的衬比度分别为1.47 dB和6.5 dB,分析得到耦合器的分束比和谐振腔的传输损耗分别为к=0.16和α=8.1 dB/cm。利用热光效应在16℃的温度变化范围内,滤波器实现了2π的相位调制,同时分析得到波导材料的热光系数约为1.28×10-5/℃。     

全电极脊形波导光传输特性

给出一种较为简便的全电极脊形波导的分析方法,即采用有效折射率方法把此金属包层脊形波导化成一个二维等效平板波导,然后利用微分法得到模的有效折射率满足的方程和吸收损耗系数的解析表达式.作为一个特例,用这种方法对SiO2全电极脊形波导光传输特性如光传播常数和损耗进行了计算, 并得到一些有益的结论.     

具有在线形貌矫正能力的组织体光学参数测量系统

针对具有复杂形貌的大面积组织体,基于空间频率域方法,提出并搭建了一种具有在线形貌矫正能力的绝对光学参数测量系统.首先利用相位轮廓术获取组织体三维表面轮廓,用余弦辐射公式法矫正由组织体表面复杂形貌引起的光照度的差异.然后,采用漫反射板代替传统方法中的参考仿体,基于空间频率域测量模式进行绝对光学参数测量,并利用提出的光学参数反演方法实现组织体吸收系数的重建.组织仿体实验结果表明,对于表面高度小于29mm的仿体,经矫正后,吸收系数的测量相对误差从60%下降到13%.     

PECVD SiC optical waveguide loss and mode characteristics

We report the fabrication of single mode SiC (silicon carbide) waveguides and the measurement of their propagation loss. By studying the effect of sidewalls scattering loss due to surface roughness and by reducing it, minimal propagation loss of 2.3 dB/cm for the TM polarization is measured in the visible at 0.633 μm. This loss can be used as a benchmark for further development of SiC microphotonic components and circuit for sensor systems in harsh environment.     

Optical time-domain reflectometry for distributed sensing of the structural strain and deformation

A unique structure of microbend optical fiber sensor (MOFS) for measuring tensile and compressive strain is described in this paper. The average measuring sensitivity for tensile strain is 35μ using 3 MOFS arrays. The repeatability and stability of MFOS are better than 18μ. The loss sensitivity of single-mode (SM) fiber and multi-mode (MM) fiber used in MOFS, as well as the relationship between the pulse width of diode laser and loss sensitivity are also studied in this paper. From these studies, some conclusions have been obtained. They are (1) the loss sensitivity and repeatability of SM fiber are better when compared to MM fiber in MOFS, and (2) the variation of pulse width of laser would only influent the signal-to-noise ratio and dynamic range, but has no contribution to loss sensitivity. Experimental results also show that loss of SM fiber highly depends on the wavelength of laser, but MM fiber has no such property. The loss of SM fiber between the wavelength of 1550 and 1310 nm is about the ratio of 6.5. Therefore, the experiments reported in this paper used a wavelength of 1310 nm to measure tensile strain and 1550 nm to measure compressive strain based on the above property of SM fiber, without changing the configuration of MOFS.     

级联菲涅尔衍射光学图像安全系统

计算机模拟验证了系统用于光学图像加密和隐藏的可行性.理论分析揭示了本系统面向应用的三个性质：相位分布的台阶数可以作为系统设计的自由度;增加系统衍射级次可以提高秘密图像的解密质量,但此时系统受到波长微变的影响也较显著;轴向位移也会产生噪音信号,其衍射距离越长,解密质量越差.     

全光可调移相器的实现机制与实验研究

本文介绍了我们在国内首次研制成功的全光可调移相器,它采用气隙距离调节法,可在光域上直接实现 ps量级的高速光信号相位(时延)调节,最大调整相位量为 600ps,插入损耗 <7dB,调节精度 <0.03ps.对实现光分组交换、光时分复用、光信号处理等具有重要意义.另外,本文还介绍了光信号相位的精密测量方法     

Application of robust color composite fringe in flip-chip solder bump 3-D measurement

This study developed a 3-D measurement system based on flip-chip solder bump, used fringes with different modulation intensities in color channels, in order to produce color composite fringe with robustness, and proposed a multi-channel composite phase unwrapping algorithm, which uses fringe modulation weights of different channels to recombine the phase information for better measurement accuracy and stability. The experimental results showed that the average measurement accuracy is 0.43μm and the standard deviation is 1.38 µm. The results thus proved that the proposed 3-D measurement system is effective in measuring a plane with a height of 50 μm. In the flip-chip solder bump measuring experiment, different fringe modulation configurations were tested to overcome the problem of reflective coefficient between the flip-chip base board and the solder bump. The proposed system has a good measurement results and robust stability in the solder bump measurement, and can be used for the measurement of 3-D information for micron flip-chip solder bump application.     

Propagation dynamics of optical vortices in Laguerre–Gaussian beams

We have calculated the propagation dynamics of an initial off-axis vortex with topological charge 1 in Laguerre–Gaussian background beams , which are examples of background beams with non-generic dislocation surfaces, on which the real and imaginary parts of the light field are zero. When initially a vortex with broad core (e.g., r-vortex) is embedded in the background beam, the dislocation surfaces are destroyed during propagation and two vortices with opposite charge are created per dislocation surface in planes perpendicular to the propagation direction. For a vortex with narrow core (e.g., point vortex) diffraction is important and leads to the birth of more than two vortices per dislocation surface. These results are also valid for other background beams with dislocation surfaces, e.g., Hermite–Gaussian and Ince–Gaussian beams. We investigated experimentally the spatial evolution of the intensity distribution of an initial off-axis vortex with narrow core and topological charge 1 in background beams. The experimental results are in good agreement with the calculated intensity distributions.     

Wideband optical phase modulator half-wave voltage measurement technique based on phase modulation optical link

We measured the half-wave voltage V_π of LiNbO₃ phase modulators in the broadband frequency range by analyzing the gain of phase modulation interference demodulation optical link. This is a new high practical value measurement method for half-wave voltage of LiNbO₃ phase modulators in wideband frequency range, and can accurately predict the nonlinear frequency characteristics of phase modulation optical link.     

Measurement of the optical absorption coefficient for liquid based on optical microfiber

An inline measuring method of the optical absorption coefficient for liquid based on optical microfiber (OM) is studied. If an OM is immersed into absorptive liquid, the additional loss of the OM will increase. We have analyzed the relationship between the additional loss of the OMs and the absorption coefficients of the liquids, and found that the OM with determinate construction will be useful for measuring the absorption coefficients of the liquid whose refractive index is lower than that of the OM. Two OM samples are prepared to measure the absorption coefficient of pure water. A supercontinuum source is launched into the OM sample which is immersed into pure water, and absorption spectrum from 1400 to 1700 nm has been achieved by monitoring the additional loss. The trend of the absorption spectrum is similar with that of the reported result, showing that the inline measurement of the optical absorption coefficient is a feasible method for those lower refractive index liquids.     

Double Security Level in Optical Communication Systems Using Combined Modulation Formats

A new optical communication system exhibiting a double security level is presented. Information coding is based on combined modulation formats of two data streams over the same optical carrier. Incoherent and coherent optical encryption algorithms are presented and are theoretically analyzed. The optical encryption method is transparent to data bit rates. Furthermore, it requires "on-line" data decoding with no possibility of recording and further processing. The incoherent scheme is very practical and can be implemented in existing optical communications systems, using currently available technology. Computer experiments of the incoherent method indicate less than 25 dB of signal to noise ratio required for 10-9 bit error rate and ineligible information decoding time of more than 10 8 years.     

Optical Bloch Oscillations of a Dual Airy Beam

We investigate the propagation of a dual Airy beam in Hermitian and non‐Hermitian waveguides, theoretically and numerically. Optical Bloch oscillations (OBOs) of the beam are demonstrated during propagation in both types of waveguides, and the numerical OBO period is found to be in accordance with the theoretical predictions. The two branches of the dual Airy beam do not display translational symmetry — the peaks will form in one branch only, due to the desynchronized Bragg reflection of the lobes. In the non‐Hermitian waveguides, the dual Airy beam will be damped or amplified during propagation — depending on the imaginary part of the complex potential, which may provide loss or gain to the beam. In the ‐symmetric‐like potential, the dual Airy beam may undergo amplification during propagation, but the total power will exhibit a stair‐like behavior. The non‐reciprocity is also exhibited by the dual Airy beam in such a potential. We believe that our research not only provides a new geometry for optical switches but also deepens the understanding of OBO in dual Airy beams.     

低偏振相关损耗聚合物光波导

表征了新合成的热光聚合物bisphenol A-aldehyde resin (BPA-resin)的独特性质。并且利用光刻和反应离子刻蚀技术(RIE)制备成功BPA-resin 聚合物的单模条波导.实验结果表明,对于TE和TM偏振,该聚合物波导在1.31 μm和1.55 μm波长下分别有低达0.43 dB/cm和0.51 dB/cm的传播损耗.在上述波长下,波导的低偏振相关损耗 (PDL)小于0.1 dB/cm.因此,是制备可调热光器件的良好导波模快.     

一种两步相移相位解算方法

提出一种将傅里叶与相移法结合的三维物体快速测量方法.通过时域提取精确的均值包络与频域滤波结合的方法预处理条纹,结合基于相位半角的两步相移,只需要两幅相移条纹图,即可得到精确的相位信息.通过仿真和实验将本文方法与现有方法进行了分析对比,实验结果证明,本文方法可以获得优于现有两步相移方法的准确度,一般测量环境下的均方根误差在3×10~(-3) rad以内.本文提出的方法对噪声和表面突变不敏感,具有鲁棒性好、运算速度快、准确度高等优点,在三维快速测量领域有较高的应用价值.     

基于双积分球和锁相放大测量的近红外多波长光学参量测量系统的研究

介绍了一种基于近红外LD光源及锁相检测技术的双积分球组织光学参量测量系统,波长范围为1 300 ~1 600 nm,正弦电调制光信号,光开关切换不同波长.提出了积分球系统改进措施,测量了散射/吸收混合溶液在1 310 nm下的光学参量,结果显示,约化散射系数和吸收系数的测量相对偏差分别<5%和10%.     

低损耗有机聚合物光波导的制备及其数字化测量技术

介绍了低损耗有机聚合物光波导的制备工艺, 并采用 Ｃ Ｃ Ｄ 摄像法对波导的传输损耗进行测量。制备了在 ６３２．８ ｎｍ 波长下传输损耗小于 ０．５ ｄ Ｂ／ｃｍ 的有机聚合物光波导     

Parametrical study of left-handed or right-handed propagation by stacking hole arrays

In this paper we analyse the recently reported structure with left-handed (LH) propagation obtained by periodically staking subwavelength hole arrays working at the extraordinary transmission (ET) resonance. A parametrical study that clarifies in more detail the equivalent inverse transmission line approach depicted in a previous work is performed. It is seen that ET is necessary to ensure a strong inductive character of the apertures. Additionally, the metal fraction of the unit cell must be large enough in order to favour the electric coupling between plates. What is more, the series capacitance is further increased by setting the plates closer. This allows considering the stacked structure as a metamaterial in that particular dimension. The experimental transmission results previously published are complemented here with a measurement of the reflection coefficient in a stack with LH propagation. These results can give rise to interesting applications such as novel lenses and other quasioptical structures.     

五层MOS光波导TE模光学特性的简化分析

应用一种简化的方法对五层MOS光波导的光学特性进行了分析,给出了TE模传播常数和吸收损耗系数的近似计算公式,并结合计算结果检验了本方法及公式的精度,为实现波导中TE_0模低损耗单模传输,讨论了某些波导参量的选择.