The Integrated Technologies For Polymer Planar Optical Waveguide Devices

In the field of photonics, Photonic Integrated Circuit(PIC)is the development trend ofthe Planar Lightwave Circuit(PLC). Polymer-based photonic integration technology hasadvantage in reducing the cost of optical waveguide devices, simplifying the fabricationprocesses, and achieving the hybrid integration. In this thesis, we focus our attentions on theintegration technology of polymer planar optical waveguide, as follows:The polymer optical waveguide material is the basis of the polymer planar opticalwaveguide devices. The loss of the material determines the overall device performance andthe integration ability. The curing time of the material determines the efficiency of the deviceprocess, the properties of the material determines the functions of the device. This thesisdemonstrated the series of UV curable NOA (Norland optical adhensive) materials in thepreparation of polymer waveguide devices and microfluidic chips. The film-formingconditions, curing conditions, flatness, etching conditions were explored. The exposureswere performed at2W/cm²for5minutes. The surface roughnesses of cured NOA materialswere less than0.8nm in a1.5μ m×1.5μ m area. In this thesis, single mode conditions of thedifferent types NOA materials were analyzed. Straight NOA polymer optical waveguideswere fabricated using ICP etching method. We got8.8dB insertion loss in a straightwaveguide with the length of2.3cm. Based on the flexibility of the NOA material, wedesigned the UV nanoimprint process. Si template and polymer SU-8template wereprepared. The ridge and quasi-rectangular waveguide structure were designed and fabricatedby UV nanoimprint process. The fabricated waveguide devices were cut using dicingmachine, etching machine, and excimer laser. By optimizing the cutting conditions, highquality endface was achieved.The development trend of the integrated polymer planar optical waveguide technologyis the integration of active devices, passive components, and microfluidic channels on thesingle chip. This thesis investigated the passive polymer optical waveguide devices, theactive polymer optical waveguide devices, microfluidic devices, and the integration of thesedevices.The polymer planar optical waveguide passive components was fabricated in this thesis,including the flexible straight waveguide device, the optical waveguide delay line device andbending waveguide device with grooves on both sides. The flexible all-polymer opticalwaveguide devices were fabricated by lift off method, and the bending polymer film deviceswere tested. The optical waveguide delay line with right angle X junction was designed, and the bending loss, junction loss, coupling loss, absorption loss of the device was simulated.The delay line device was prepared by SU-8material using wet etching method. Relevantparameters of the devices were tested. Optical waveguide delay line devices with right angleX junctions were more compact, and the delay time between adjacent waveguides hadpotential applications in the X-band radar. In order to reduce the bending loss of thewaveguide, grooves were prepared on both sides of the bending ridge waveguide structure.The test results demonstrats that the grooves can reduce the bending loss of the ridgewaveguide.Microfluidic chip plays an important role in the integration technology of polymerplanar optofluidic devices. Using high-quality groove prepared by nanoimprint process, wefabricated the microfluidic chips. Different cross-section microchannels (5-100micronswidth,6-micron height) were prepared. Microfluidic method of preparing opticalwaveguides can be described as filling in the pores within the polymer material and curingthe material. Rectangular waveguide was obtained by this method. In this thesis, themicrofluidic channels and optical waveguides were integrated in the same plane. The SU-8groove was first fabricated. And then, the aluminum mask was prepared. At last, the grooveswere packaged and the SU-8optical waveguide were photobleached. The optofluidic chipswere tested at1550nm. The insertion loss of photobleaching straight waveguide (notpolished) was24dB (intersection with36micro-channels).Integration technologies in the active optical waveguide devices were also discussed.Electrodes and waveguides of active waveguide device were fabricated. ITO electrode andAl electrode were selected in the fabrication. BP212and BP218photoresist were selected asthe mask during wet etching preparation. The BP218mask was better than BP212mask. ITOelectrodes with the width of6microns were prepared by BP218mask. Al electrodes wereprepared, on the film and the Si substrate, respectively. Lift off method was introduced,because of the different adhesion of Al between theSiO₂substrate and the polymer.Aluminum was deposited on the Si wafer by thermal evaporation. The mask was fabricatedby wet-etching. Then we spun coated NOA63material, curved it at365-nm wavelength(2W/cm²) for6minutes and lift off the mask. The method can avoid the thermal affection tothe polymer film during the evaporation and chemical affection to the polymer film duringthe photoresist removing process. Aluminum electrodes were also prepared on Si substrate.Si substrates were first etched. And then aluminum electrodes were evaporated. The finalstep was removing the photoresist. By this method,2μm width aluminum electrodes wereprepared on Si substrate. The Electro-optical core material waveguides and the amplifier core materials waveguides were prepared. In this thesis, electro-optic properties hybridmaterial waveguides with1μ m×1μ m dimension were prepared by nanoimprinttechnology. Different kinds of the amplifier core materials were filled in the flexible groovesto fabricate flexible optical waveguide amplifiers. Flexible thermo-optic switches using theNOA material and nanoimprint technology were fabricated and tested, the switching timewas350μs.Organic materials and inorganic materials are integrated to realize the losscompensation, the amplification in selected region, waveguide sensor, as well as theintegration of flexible waveguide. Erbium-doped phosphate glass was synthesized in thethesis. Glass waveguides were prepared by ion exchange technology. Loss compensationstructures were designed and simulated. From the experimental point of view, the feasibilityof the integration of organic polymer waveguides and inorganic ion exchange waveguidewas discussed.Finally, Preliminary progresses about the integrated optical waveguide technologieswere explored. Polymer gratings were fabricated using nanoimprint technology.45degreeangle endfaces of polymer films were prepared by excimer laser, which can be used in thefabrication of the polymer reflector in the vertical integration of light sources, sensors andwaveguide. Direct curing technology provided a fast and low-cost way to fabricate polymeroptical waveguide device.