利用稜鏡光柵製作高密度分波解多工系統和分色贗無繞射相位繞射元件之研究

Abstract

本論文的研究工作共分為兩部份，分別為具有特殊功能的繞射相位元件與自由空間型的高密度分波解多工系統的研究。 在論文的第一部份，將說明具有特殊功能繞射相位元件的研究工作，我們分別利用共軛梯度法與振幅相位重建演算法設計出能產生三色贗無繞射光束的繞射相位元件，再利用黃光微影製程與反應離子蝕刻技術製作出所需的繞射元件，最後利用數值方法作各項誤差分析，實驗量測結果顯示所製作的繞射元件具有所要求的光學特性，例如在一定的軸向距離內能產生六段贗無繞射光束並且在每一段光束中只存在一種波長。 在論文的第二部份，將說明自由空間型高密度分波解多工系統的研究工作，此系統具有16個通道並且每個通道中心波長差為0.8nm。首先我們利用KRS-5紅外材料設計出稜鏡光柵作為自由空間型的分波解多工器，利用精密鑽石微加工車床直接在稜鏡表面刻劃出閃耀光柵，此光學稜鏡與閃耀光柵的複合元件稱為稜鏡光柵。為了估算製程誤差對光學特性的影響，我們利用數值方法計算出在各種不同的製程誤差下分波解多工器的光學特性，由模擬計算與實驗量測結果可知所設計的分波解多工器其光學特性為極化無關並且具有好的光學效率與訊噪比。其次，我們設計出此分波解多工器與商用光纖陣列間的耦合裝置，利用黃光微影製程與感應耦合電漿蝕刻系統在矽基板上製作出光管陣列，再使用高溫氧化法在光管陣列的表面氧化出一層抗反射薄膜以降低光管的表面損耗。最後，我們結合了稜鏡光柵與光管陣列成為一個完整的分波解多工系統並量測其光學特性，量測結果顯示此系統具有預期的光學特性，此分波解多工系統的每個通道的介入損失約為2.4 dB，而相鄰通道的串話約為 -17dB。

In this thesis, there are two parts, one describes about a free-space dense wavelength division demultiplexing system（DWDDM） and the other describes a diffractive phase element （DPE）with special function. In the first part, the design and fabrication of the DPE that synthesizes three-color psudo-nondiffracting beams (PNDBs) is described. This DPE is designed with the amplitude-phase retrieval method and the conjugate gradient method. The designed element is fabricated by using optical contact lithography and reactive-ion etching (RIE). The influences of several errors on the optical properties of the fabricated element are analyzed with the numerical analysis. Measurements demonstrate that the fabricated DPE has the desired function, i.e., forming six-segment PNDB over a finite axial region and monochromatic in each segment. In the second part, a free-space dense wavelength division-demultiplexing (DWDDM) system in the fiber communication is proposed. The system has sixteen channels with wavelength spacing of 0.8nm in the C band wavelength region. Firstly, the design and fabrication of a low-loss demultiplexer with a KRS-5 grism structure for this system is carried out. This demultiplexer has been successfully fabricated by a precise plunge-cut diamond-turning technology. The influences of the process errors on the optical properties of the device are discussed. Numerical calculations and measurements indicate that this demultiplexer is polarization-independent and has higher optical efficiency and signal to noise ratio (SNR). Secondly, a light pipe array as a coupling system between the demultiplexer and a commercial fiber array has been designed and fabricated on a silicon-on-insulator wafer by using optical contact lithography and inductively coupled plasma-reactive-ion etching. In order to reduce the insertion loss, an anti-reflection coating is formed on the end surfaces of light pipe array with the thermal oxidation method. Finally, the performances of the DWDDM system that consists of the fabricated demultiplexer and light pipe array are measured. The experimental measurements demonstrate that this demultiplexing system shows good optical performance. The insertion loss for each channel is about 2.4 dB, and the next-neighbor cross talk is lower then -17dB.