溶胶－凝胶法在平面光波导薄膜中的应用

溶胶－凝胶工艺在薄膜制备方面有其独特的优越性，如工艺过程温度低、成分均匀、纯度高、成膜面积大等。近年来已在薄膜制备方面得到广泛应用。本文简要地综述了溶胶－凝胶工艺在制备平面光波导薄膜中的应用。     

溶胶—凝胶法在平面光波导薄膜中的应用

溶胶－凝胶工艺在薄膜制备方面有其独特的优越性，如工艺过程温度低，成分均匀、纯度高，成膜面积大等。近年来已在薄膜制备方面得到广泛应用。本文简要地了溶胶－凝胶工艺在制备平面光波导薄膜中的应用。     

利用有机-无机溶胶-凝胶方法制备平面波导环形谐振腔

采用简单的有机-无机混合的溶胶-凝胶方法制备了折射率在一定范围内可调的波导材料,并利用其制备了平面波导环形谐振腔器件。波导结构呈现倒脊形,其制备工艺首先是利用感应耦合等离子体刻蚀技术(ICP)在二氧化硅衬底上刻蚀波导结构的凹槽,然后再沉积波导薄膜。利用光谱仪对器件的传输特性进行了测量,观测到具有10 dB对比度,自由光谱范围0.182 nm周期性谐振现象,结合环形谐振腔的传输特性,得到环形腔具有较低的传输损耗1.7 dB/cm。同时对环形谐振腔的温度特性进行了测量,得出波导材料的热光系数为-1.54×10-4/℃。     

激光直写法制备条形光波导中的功率密度阈值

采用溶胶-凝胶法(sol-gel)在Si基SiO2衬底上制备了SiO2-TiO2芯层薄膜,构成了以SiO2为下包层,空气为上包层的平面光波导。利用光纤激光器对平面波导的芯层进行直写,结合后续的化学腐蚀工艺得到了SiO2-TiO2条形光波导,并着重研究了激光直写波导过程中存在的功率密度阈值以及阈值随薄膜预热处理温度的变化关系。研究结果表明,激光直写SiO2-TiO2波导存在起始收缩阈值和烧蚀损伤阈值;随着薄膜热处理温度的提高,两个阈值同时增大,其中损伤阈值的增大趋势要大于收缩阈值;因而薄膜可承受的直写光斑直径变小,所得波导宽度显著减小。最后对直写制得条形光波导的导光性能作了测试分析,验证了波导的三维导光性。     

化学修饰溶胶-凝胶法制备功能薄膜微细图形

介绍了一种功能薄膜微细图形制备新方法—化学修饰溶胶-凝胶法。该方法的特点是在溶胶-凝胶制膜过程中引入化学修饰法,从而赋予薄膜以感光特性。利用该特性制备了微细图形,简化了工艺流程,并可以获得具有微米级的功能薄膜微细图形。概述了这种方法制备薄膜微细图形的原理、工艺流程以及主要影响因素,并对其在光波导薄膜、铁电薄膜和透明导电氧化物薄膜微细图形制备领域的研究情况进行了综合评述。最后对该方法的研究趋势进行了展望。     

波导的溶胶-凝胶工艺

对于光学波导与导波设备、电路的制造而言，溶胶-凝胶工艺的出现不失为一种有效途径。特别是集成光学有源器件及电路中掺活性掺杂物(如钕、铒、铈)。本文回顾了基于溶胶-凝胶工艺的有源器件、电路的最新研究。对于光学放大器中的激活溶胶-凝胶薄膜的模拟分析，我们提出激光器原子磁化理论及其速率方程，适当考虑了波导参数。采用波束传播法研究激活掺杂溶胶-凝胶薄膜设备(如直线波导、丫形支管、定向耦合器)的传播及增益特性。也在研究掺铈薄膜中布拉格光栅的形成，在微电机系统(MEMS)的未来应用也在研究中，可采用溶胶-凝胶工艺形成光层．并通过机械作用加以控制。     

低损耗玻璃光波导的溶胶-凝胶法制备

采用溶胶－凝胶（Ｓｏｌ－ｇｅｌ）技术制备了ＳｉＯ２－ＴｉＯ２低损耗平面光波导,在６３３ｎｍ处的传输损耗为０．５７ｄＢ／ｃｍ。同时在硅基板上制备了脊型Ｙ形波导分束器,分束比为１１。     

平面波导光传感器的研究进展

高灵敏度的光传感技术在工业过程控制、环境监测、食品安全、国家安全等领域具有重要的应用.随着平面光集成制备技术的发展,光传感器件也从研究开发光纤传感器拓展到便于集成的平面波导光传感器,特别是采用多孔、易掺杂的溶胶一凝胶材料作为化学、生物医学探测的光传感媒介.综述了平而波导光传感器的研究现状与发展趋势,讨论了器件的光传感原理与结构,介绍了其在化学、生物医学、环境检测等方面的虚用.     

SnO2光透射率气敏薄膜的制备

采用溶胶-凝胶技术,利用旋转涂膜法制备非晶态二氧化锡薄膜,常温下在含有CO的气氛中光通过薄膜的透射率变大,对CO有较高的灵敏度.对制备过程中出现的实验现象、制备机理及薄膜的结构和特性进行了研究.     

一种有机聚合物光波导的制备及性能研究

溶胶凝胶法制备了聚甲基丙烯酸甲酯(PMMA)掺杂偶氮类化合物分散红1(DR1)薄膜波导,并通过对薄膜厚度、折射率以及紫外-可见吸收谱的测量,分析了波导薄膜的性能。通过使用棱镜薄膜耦合装置激发薄膜波导的导模,观察导模激发情况。利用m线光谱学测量并计算了导模的同步角,计算了波导有效折射率,并在理论上分析了波导的一些重要参数。     

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感特性。对传感机制进行了讨论。     

热键合双包层平板波导激光器的研究进展

介绍了热键合双包层平板波导激光器的研究进展,包括热键合技术的优越性,双包层平板波导的新思想,集成可饱和吸收体的被动调Q波导激光器。     

A novel processing technique to fabricate planar InGaAsP/InP electroabsorption waveguide modulators

A novel processing technique has been developed to fabricate planar electroabsorption waveguide modulators in compound semiconductor heterostructures. The lateral confinement of light is achieved by introducing controllable, reproducible, and stable stresses into semiconductor heterostructures using WNi surface stressor stripes, which also serve as electrodes for the waveguide modulators. Self-aligned helium implantation is employed to achieve electrical isolation using the Stressors as the templates for the ion masks. An increase as large as 33000 times has been obtained in the dc resistance between the neighboring waveguide modulators 25 μm apart. Propagation loss of 1.7 dB/cm is observed in the photoelastic waveguides at a wavelength of 1.53 μm following the He implantation. A post-implant thermal annealing at 310°C for 40 min increases the dc resistance between the neighboring devices to the maximum value, and at the same time reduces the optical loss to its value before ion implantation (less than 1 dB/cm). Using a combination of the photoelastic effect and helium implantation, planar InGaAsP/InP Franz-Keldysh-effect waveguide modulators 430 μm long with a 10 dB extinction ratio at 3 V for the TM mode have been fabricated. Planar electroabsorption quantum-confined Stark effect waveguide modulators have also been demonstrated. This planar device processing technique may prove valuable in future photonic integrated circuit technology.     

Improvements of the two-dimensional FDTD method for the simulationof normal- and superconducting planar waveguides using time seriesanalysis

Time-domain simulation results of two-dimensional (2-D) planar waveguide finite-difference time-domain (FDTD) analysis are normally analyzed using Fourier transform. The introduced method of time series analysis to extract propagation and attenuation constants reduces the desired computation time drastically. Additionally, a nonequidistant discretization together with an adequate excitation technique is used to reduce the number of spatial grid points. Therefore, it is possible to simulate normal- and superconducting planar waveguide structures with very thin conductors and small dimensions, as they are used in MMIC technology. The simulation results are compared with measurements and show good agreement     

On the numerical errors induced by the space-time discretization in the LE-FDTD method

In this work, the accuracy of the lumped element finite-difference time-domain (LE-FDTD) method is discussed in the particular case of a planar distribution of equal resistors. Following the von Neumann technique and assuming a uniform grid, the effective impedance of the lumped resistor has been rigorously derived in a closed form. The result obtained has been compared with the LE-FDTD simulation of a simple test structure. This structure consists of an infinitely long parallel-plate waveguide loaded with the planar distribution of resistors. The excellent agreement obtained validates the approach showing a dependence of the effective resistor impedance on spatial and temporal discretization steps.     

Realization of dielectric loaded waveguide filter with substrate integrated waveguide technique based on incorporation of two substrates with different relative permittivity

In this paper a new structure based on substrate integrated waveguide (SIW), called incorporated substrate integrated waveguide (ISIW), has been used to implement the dielectric loaded waveguide filter in planar structure. Conventional waveguide filter and dielectric loaded waveguide filter have been realized with SIW and ISIW technique, respectively. The use of ISIW structure has reduced the size of the filter, required precision in designing process and the cost of manufacturing process, at the cost of increasing the losses. Thus, while the size of filter and the cost of manufacturing process reduce significantly, there is no need to build the particular dielectric material as resonator and integration with other microstrip devices will be much easier too. Two different excitation mechanism have been considered to cancel the spurious response in the desired frequency band. The SIW and ISIW filters have been fabricated and fairly compared with waveguide filters. Advantages and disadvantages of ISIW structure have been scrutinized in detail. Good agreement between the simulated and measured frequency response of proposed filters has been shown.     

Optimization of planar devices by the finite element method

The finite-element method is an efficient and flexible way of computing the scattering parameters of N-port planar devices (microstrip, stripline, rectangular waveguide, etc.). In addition, it can provide, at little extra cost, the sensitivity of scattering parameters to changes in the shape of the device. such information can lead to a faster automatic optimization of the shape. This approach has been implemented with high-order, triangular finite elements and the Broyden-Fletcher-Goldfarb-Shanno optimization scheme. Sensitivities were computed for an empty parallel-plate waveguide and for a rectangular waveguide containing a dielectric slab. The agreement with analytical solutions was excellent. The method was used to determine the optimum shape of a microstrip 3-dB hybrid and was found to require far fewer analyses than a previous technique     

Simulation of waveguide birefringence by beam propagation method

It is demonstrated that, by modifying the waveguide geometry, the beam-propagation method (BPM) can be extended to determine the mode indexes of both polarizations. Such an approach has been implemented into BPM routines. It can be used to determine the birefringence in waveguide structures. The same approach is also applicable in other waveguide simulation programs based on the scalar field approximation. The operational principle and numerical results for planar waveguides are presented, and the extension of this technique to channel waveguides is discussed.<>     

Waveguide Technique for the Calibration of Miniature Implantable Electric-Field Probes for Use in Microwave-Bioeffects Studies

A new S-band waveguide technique has been developed for the calibration of miniature probes used in determining electric fields in biological tissues at 2.45 GHz. A section of waveguide is filled with tissue-equivalent liquid separated from the air-filled waveguide by a very thin (0.25-mm) planar dielectric spacer. The probe response is measured as a function of position on each side of the spacer and extrapolated to the interface. The ratio of probe response in air to that in test liquid is then determined assuming continuity of tangential E-field across the spacer. In the water-glycerol solution modelling wet tissue, the probes are 3.0+-0.6 times more sensitive to E/sup 2/ than in air. A wide variety of both wet and dry tissues may be simulated using liquids of different dielectric properties--a check on the properties is provided by comparing the measured depth of penetration of the wave in the liquid with the calculated value. Problems using the probes in biological tissues are also discussed.