| 摘要: | 矽光子技術利用積體光路取代傳統電路，提供了一個高傳輸速度、寬頻寬、低損耗的資料傳輸渠道。而群速度色散在光通訊、非線性光學、超快光學等領域中扮演一個重要的角色。本論文透過在氮化矽波導上疊加不同比例之聚合物披覆層，以達到靈活調製色散的目的。首先，利用有限元法來模擬不同波導截面設計之波導色散，並觀察在不同寬度、高度和披覆層材料下波導色散的變化。第二部分為色散量測系統之建立，在本論文研究中利用光纖之馬赫－陳爾德干涉儀來作為參考頻譜，以確認可調式雷射在掃描時穩定度，並且建立一個解析度優於雷射之頻率軸。
在實驗上，將空氣、氧化物和聚合物披覆層疊加在共振腔上，並對波導色散進行比較。在波導上疊加聚合物披覆層後，可以將波導色散從−143 ps/nm-km調製成−257 ps/nm-km。除此之外，透過去除聚合物的方法來實現可重構之聚合物披覆層，波導色散會還原至初始色散大小，以及對品質因子而言也沒有明顯的影響。接著利用微影技術在環形波導上疊加不同覆蓋比例之披覆層。測得的色散與覆蓋比例呈線性相關，與模擬數據具有良好的一致性。因此可以通過控制聚合物披覆層的覆蓋比例，使得波導色散在上述色散變化區間內進行調製。最後，將波導高度提升至700 nm的波導，其色散為66 ps/nm-km，為異常色散。接著在波導上疊加聚合物披覆層，其波導色散大小為-508 ps/nm-km，為正常色散。因此可以透過疊加聚合物披覆層的方式來使得具異常色散之共振腔調製成正常色散。
本論文研究提供一個靈活、新穎的方法來製造一具多功能性的積體光路，以滿足不同應用對色散的要求。
;In silicon photonics, integrated optical circuit replaces electrical circuit, and it provide a data transmission channel with high transmission speed, wide bandwidth, and low loss. Moreover, group velocity dispersion (GVD) is an important physical quantity in many photonic applications, such as optical communication, nonlinear optics, and ultrafast optics. In this thesis, we propose a flexible way to engineer waveguide dispersion with patterning different coverage ratios of polymer cladding layer on silicon nitride waveguides. First, the finite element method is used to simulate the waveguide dispersion of different waveguide cross-section designs and to observe the changes of the waveguide dispersion under different widths, heights, and cladding materials. The second part is the establishment of the dispersion measurement system. Fiber-based Mach-Zehnder interferometer is used as the reference spectrum to confirm the stability of the tunable laser during scanning and to build a calibrated frequency axis, which has a better resolution than that of the laser.
Experimentally, air, oxide and polymer cladding layers are coated on the microring resonaters and the waveguide dispersion is measured accordingly. The waveguide dispersion can be tuned from −143 ps/nm-km to −257 ps/nm-km by integrating the SU-8 polymer as the outer cladding layer. In order to realize the reconstructability of polymer cladding, we remove the polymer cladding layer. After stripping the polymer layer, the waveguide dispersion can be recovered to the original value, and there is no obvious impact on the quality factor. In addition, different coverage ratios of cladding layer are patterned on the microrings with traditional UV contact lithography. The measured dispersion shows linear dependence to the coverage ratio, showing good agreement with the simulated data. Thus, the waveguide dispersion can be engineered within a varied dispersion range by controlling the coverage ratio of the polymer cladding layer. Last, by increasing the waveguide height to 700 nm, the measured dispersion is tailored to be 66 ps/nm-km, which is in anomalous dispersion. After 100% coverage ratio of polymer cladding layer is patterned on microring, the measured dispersion is tuned to be -508 ps/nm-km, which is in normal dispersion. This provides a flexible way to engineer the dispersion. The dispersion can be tuned from anomalous to normal by superimposing different coverage ratios of polymer cladding layer on the waveguide.
The research presented in this thesis provides a flexible and novel approach to fabricate a multifunctional integrated optical circuit to meet the dispersion requirements of different applications. |
