微流控集成光波导光开关的研究

【作者】 黄腾超；

【导师】 刘旭；

【作者基本信息】 浙江大学 ， 光学工程， 2005， 博士

【摘要】 光开关是现代光通讯系统和传感器网络的关键器件,利用微机电系统（MEMS）技术的集成光波导光开关以其体积小、性能高、成本低等优点成为众多解决方案中有力的竞争者之一。本论文以微流控集成光波导光开关为研究对象,从理论与实际工艺制备等方面对其进行探索。 论文将微流控精确,迅速的特点与MEMS批量制造优势相结合,从理论上提出了一种新型热驱动微流控光开关设计,将波导结构和开关功能结构集成在一个基底结构上,使器件阵列具有体积微小,易集成,可靠性好的优点。依据热力学定理和微流体特性,创新地提出了利用表面张力作为光开关器件的驱动力,控制折射率匹配的液体在微通道内秩序流动的方案,提出并建立了流体在微通道内运动的热毛细效应模型。 论文阐述了离子交换制作光波导的一般理论,利用有限差分法研究了离子扩散波导内部离子浓度分布,折射率分布。利用条形函数法分析了电磁波在扩散光波导中的传播理论,较为系统地研究了制备时扩散温度,扩散时间等因素对波导光学性能的影响。并以此为基础,通过K⁺—Na⁺二次热交换的方法制备了平面和条形光波导,控制扩散温度和扩散时间,制得了不同工艺条件下的光波导。 在光开关器件的制作工艺中,论文首次提出了“SiO₂薄膜辅助硅—玻璃热键合技术”,SiO₂作为辅助键合层,减小了由于玻璃、硅材料热膨胀差异带来的内部应力,该技术对硅—玻璃直接键合技术是一项补充。微加热器件的设计制作过程中,论文中提出了硅基底上二次硼扩散制作微电阻的方案,微电阻通入I=40mA,占空比1∶4的电流脉冲时,可以在表面得到100K的温度差。论文创新性地提出了利用压力精确控制微量液体注入液槽的设计方法,解决了微量折射率匹配液进入液槽的技术问题。论文详细阐述了利用湿法腐蚀工艺制备液槽的过程,探索并测量了刻蚀过程中,腐蚀液成分,腐蚀时间,掩膜材料对腐蚀的影响。 制得的光开关插入损耗为2.9dB,开关响应时间为110ms。论文分析了影响其指标的机理和因素。 本论文开展了微流控集成光波导光开关的研究,总结了制作器件的工艺过程当中的一些重要现象和效应。对下一步的工作进行了展望,确定了改进方向与措施。更多还原

【Abstract】 Optical switch is the key device of modern optical communication and sensor systems. With the advantages of small volume, high performance, and low cost, the integrated optical waveguide switch employing Micro-Electro-Mechanical systems (MEMS) technology is one of most challenging idea among all optical switch solution. This thesis focused on the related theory of the micro-fluidic driving MEMS integrated optical waveguide switches as well as its fabrication techniques.By combining with the precise and stabile characteristics of micro-fluidic driving and the batch fabrication advantage of the MEMS technology, a novel micro-fluidic waveguide optical switch is developed firstly. It is a kind of optical switch with a micro actuator fabricated in a planar lightwave circuit (PLC) by micromachining. This device consists of an upper glass substrate and an intersecting waveguide substrate that has a groove at crossing point and a pair of micro heaters. An innovative driving method that uses a thermocapillarity effect and the characteristic of microfluid flowing in micro channel is applied in this optical switch. The refractive-index-matching liquid in the groove is driven due to surface-tension variation caused by heating (thermocapillarity). In this thesis, a model of thermocapillarity effect of micro fluid flowing in micro channel is setup.The conventional theory of the ion-exchanged making optical waveguide was introduced, and the ion concentration spread, refractive index spread in waveguide is calculated by FDTD method. The theory of electromagnetic wave propagating in ion-exchanged optical waveguide is analyzed by numerical strip distributed transfer function method. The influence of diffusion temperature and diffusion time on optical waveguide’s performance is analyzed in detail. Based on this theory, plane and strip optical waveguides were fabricated by K+-Na+ binary ion-exchanged method under new processing condition.During the fabrication process of optical switch, the technique of "Silicon-Glass Thermal Bonding with SiO2 Film Assist" is proposed for the first time. In this technology, the presence of thermal grown SiO2 film reduces the induced stress due to the difference of silicon and glass in the thermal expansion coefficient and thermal conduct coefficient.An innovative technique of batch injection of a very small amount of liquid by pressure is proposed. And two steps Rapid Thermal Boron Diffusion (RTBD) from borosilicate glass (BSG) was adopted to fabricate the micro resistor. The resistor can make a temperature difference about 100 degrees during 0.1s with a pulsewidth of 200us for 0.04A current pulses.To fabricate highly accurate deep-groove, a series of comparable experiments are done to observe the etching effects with different etching solutions, at the same time the effects of different etching conditions, such as etching temperature, rabbling mechanism, cleaning interval on the etching results are investigated and studied experimentally.In combination with previously developed highly accurate deep-groove fabrication, batch injection of a very small amount of liquid, and high-performance sealing, optical switch device with high performance were achieved. The insertion loss of switch is about 2.9dB and the switch time is 110ms. The factors that influence switch performance are analyzed in the thesis.Research on microfiuidic integrated optical switches is proposed in this thesis. The important effects in device design and fabrication process are summarized. The test results were analyzed and the further measures to improve the performance were also discussed.更多还原