| Summary: | 碩士 === 國立成功大學 === 微電子工程研究所碩博士班 === 97 === In this master thesis, we have successfully fabricated reproducible and low-cost optical waveguide devices in glass such as N-BK7 by ion-exchange technique. The concept of implementing buried waveguides as components of integrated optics devices is first pursued with a goal of minimizing the propagation loss. The entire process is assisted by applying the electric field to bury the waveguides 10μm into the glass substrate. Afterward, novel 1x2 MMI devices by cascading a multiple number of MMI stages are designed and built via the molten salt ion-exchange method. The composition of the melt solution is made up of AgNO3 and NaNO3 with the ratio of 0.02 to 1. One of the most important reasons to adopt the cascade structure is that the overall MMI length (L) of cascade structure could be made shorter compared to the conventional 1 x 2 MMI, with an extent of 50% shorter.
Finally, two different designs of MMI waveguides are incorporated as components of the MMI-based Mach-Zehnder interferometer (MZI) modulators. Our measurement result will show that the MMI-MZI modulators with cascaded MMI stages do have lower modulation voltages or Vπ×L; one of key figures of merit demonstrating the fabricated devices with comparably lower power consumption. Furthermore, the cascaded structure also has better electric characteristic compared to that of the original structure. Based on the measurement results obtained, the normalized optical power decays down to 0 once the Vπ is attained, which could be predicted beforehand by simulation. In addition, the original and cascaded MMI-MZI structures both deliver power attenuation close to 20dB. Among the devices studied, the highest attenuation could reach up to 31dB, which is highly beneficial for their functional role as variable attenuators.
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