| Summary: | 碩士 === 國立交通大學 === 電子研究所 === 105 === In this study, the inverted taper couplers and several types of crossing devices based on silicon nitride (SiN) waveguides have been investigated. We used beam propagation method (BPM) to simulate the characteristics of the inverted taper couplers. The inverted taper couplers with 0.1 and 0.2 μm tip widths have coupling efficiencies of 0.872 and 0.707, respectively, from 5-μm-MFD fiber to 0.5-μm-width and 1-μm-thickness waveguide at the wavelength 1550 nm. The inverted taper couplers with 0.2-μm tip width were fabricated and characterized. The coupling loss of the inverted taper coupler was 6.9±0.79 dB in C band, which was not as good as expected. The fabrication imperfection of high aspect ratio waveguides might be the reason for the considerable loss. However, the couplers had rather flat coupling efficiency spectrum over the C band, proving its advantage of having broad operation band. Besides, we also simulated and fabricated the couplers with different taper lengths, and the results showed that a 100-μm taper length was long enough for efficient mode conversion. We also fabricated several types of crossing devices. The insertion losses of two types of crossing devices were in the range of 0.1 to 0.3 dB in C band. For the ring notch filter, the free spectrum range (FSR) was doubled to 17.6 nm in C band.
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