Microfluidic Integrated Optical Waveguide Optical Switch

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.