Pulley-Type Microring Resonator with High Quality Factor

We propose the guidelines to design the high Q-factor microring resonators. First, by wrapping the curved waveguide around the microring to form the pulley coupler, the bending loss can be effectively decreased. Second, the large difference of propagation constant, Δβ, between the microring and the bus waveguide can maintain the propagating light in the microring. Third, the critical coupling can be optimized by adjusting the bus waveguide width to increase the Q-factor. For demonstrating the performance of the designed high Q microring resonator, the pulley-microring resonator and the grating coupler are fabricated on the silicon-on-insulator substrate by using the E-beam lithography and the reactive-ion etching. The Q-factor can be obtained as high as 1.73×10^5. In the literature, the microring resonator with the radius of 20 μm constructed by the pulley coupler, such that pulley-type microring resonator can provide the high Q-factor from 2×10^4 to 6×10^5. In this thesis, the pulley-type microring resonator with high Q-factor of 1.73×10^5 and with the smaller radius of 4.43 μm is proposed and demonstrated. The high Q-factor pulley-type microring resonator is obtained by adjusting the bus waveguide width. This indicates that the pulley-type microring resonator is suitable for the miniaturization of the optical integrated circuit.

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並列摘要

本研究提出一個設計及優化環型共振腔的方法。首先，在環形共振腔外圍包裹一彎曲載波波導可形成滑輪型耦合器並有效降低環形共振腔的彎曲損耗。第二，載波波導與環形共振腔之間的傳遞常數（Δβ）愈大愈可以將光儲存在環形共振腔中。第三，可以藉由調整載波波導的寬度快速達到臨界耦合以增加Q值。為了實現高Q值的積體化元件，我們使用電子束微影及反應式離子蝕刻將滑輪式環形共振腔及光柵耦合器定義在SOI晶片上。經由量測可以得到的Q值約1.73×10^5。目前文獻中，具有高Q值的滑輪型環形共振腔其半徑約在20 μm，而Q值約落在2×10^4到6×10^5之間。因此在本文中提出具有高Q值（1.73×10^5）和小體積（半徑4.43 μm）的滑輪式環形共振腔，藉由改變載波波導的寬度可以在不增加環形共振腔半徑的前提之下而提高Q值。相較之下，本文提出滑輪式環形共振腔的半徑約為上述文獻的22.5%，且具有相當高的Q值，因此滑輪式環形共振腔是相當適合積體化的光學元件。

並列關鍵字

滑輪式；環形共振腔；品質因子

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