平面波導式凹面光柵元件之設計、分析與應用

Abstract

本論文研究平頂（flat-top）頻譜響應平面波導式凹面光柵之設計與探討製程誤差之影響。另外，介電質反射面（dielectric mirrors）用於平面波導式凹面光柵之反射面和一種新型的光塞取多工器（optical add/drop multiplexer）結合平面波導式凹面光柵也被提出與設計。平面波導式凹面光柵解多工器之平頂頻譜響應，是以三聚焦點(three-focal-point)和五聚焦點(five-focal-point)方法設計。論文中，詳盡討論波導結構和元件的設計流程。三聚焦點的設計方法可以得到最大-1-dB通帶寬度(passband width)為27.19 GHz和最小漣波值(ripple)為5.00 × 10 E-3 dB。五聚焦點的設計方法以多目標函數基因演算法(multiobjective genetic algorithm)做最佳化，得到最大-1-dB通帶寬度為30.53 GHz和最小漣波值為1.09 × 10 E-4 dB。製程誤差所引起隨機相位和強度的誤差對於元件的影響也有加以評估。為了在光柵反射面達到高反射及低偏振依存性損耗（polarization-dependent loss），介電質反射面用於平面波導式凹面光柵的反射面被提出。當使用其設計時，其偏振依存性損耗可以小於0.05 dB。一種新型的光塞取多工器（optical add/drop multiplexer）結合平面波導式凹面光柵被提出，其設計目標為達到較高的自由頻譜範圍(free spectral range)以及較小的裸片尺寸（die size）。其設計的裸片尺寸為70 × 61 mm^2，而消光比(extinction ratio)可以小於-59.20 dB。

The design and the impact of the fabrication errors for a flat-top planar waveguide concave grating demultiplexer have been investigated. A planar waveguide concave grating employing dielectric mirrors and a novel optical add-drop multiplexer (OADM) employing a planar waveguide concave grating have been proposed. For the design of a flat-top grating based planar waveguide demultiplexer, the three-focal-point and five-focal-point methods are introduced and analyzed with a design example. The structures and design procedures are discussed in detail. For the three-focal-point method, the highest -1-dB passband width of 27.19 GHz and the lowest ripple of 5.00 × 10 E-3 dB are achieved. For the five-focal-point method optimized with the multiobjective genetic algorithm, the highest -1-dB passband width of 30.53 GHz and the lowest ripple of 1.09 × 10 E-4 dB are achieved. The impact of fabrication errors, resulting in the random phase and amplitude errors, is also estimated. To yield a high-reflectance and low polarization-dependent loss (PDL), a planar waveguide concave grating employing dielectric mirrors is proposed. The PDL is below 0.05 dB when the proposed dielectric mirrors are used. A novel OADM employing a planar waveguide concave grating for the higher free spectral range (FSR) and smaller die size is proposed. The total die size is 70 × 61 mm^2 with the extinction ratios less than -59.20 dB.