積體光碟元件中聚焦光柵之研究

Abstract

在本論文中, 我們分析聚焦光柵的像差特性並探討其在積體光碟讀取元件 應用上的可行性o理想的聚焦光柵聚焦效果能達繞射極限, 但因製造誤差 導致像差的產生因而使聚焦光點加大o 在本論文中, 我們分析其像差特 性, 再利用 Marechal的條件求取誤差的容忍值o 在設計及分析上, 我們 考慮波在波導和光柵中傳播常數的不同o 有關聚焦光柵的理論如: 光柵製 造方程,聚焦特性, 像差特性, 傳播常數和輻射因子等有詳細討論, 像差 特性的模擬結果和誤差容忍值亦被提及, 聚焦光柵的設計流程, 例子及元 件品質也有探討o 最後, 我們對研究成果做個結論和未來展望o In this thesis, we analyzed the aberration characteristics of the focusing grating coupler (FGC) and investigated the feasibility of this device for integrated-optic disk pickup (IODPU) head applications. An ideal FGC gives a focused spot of diffracted-limited size. However, the fabrication errors result in the aberrations and increase the spot size. In our study we analyzed the aberration characteristics of the FGC and use the Marechal's condition to calculate the tolerances of the fabrication errors. The mode index difference between the waves propagating in the waveguide and grating region was considered in our grating pattern equation for device design and image performance evaluation. Basic theories to describe pattern equation, focusing characteristics, aberration characteristics, mode index and radiation decay factor of the FGC were described in detail. Simulation results of aberration characteristics due to fabrication errors and deviation tolerance of each device parameter were presented. The design procedure of a FGC is given. A design example and its device performance are discussed. Finally, conclusions and recommendations are given.