臺灣博碩士論文加值系統

長週期光纖光柵(Long-period fiber grating, LPFG)已被廣泛研究和應用在光纖通訊系統上，但是光纖在元件的實現上會有幾何形狀和材料選擇上的限制，為了要消除光纖在製作上的限制和實現元件積體化，長週期波導光柵(Long period waveguide grating, LPWG)已被提出研究和實現，然而隨著積體光學電路的進步，由於傳統的光柵濾波器之單一的工作波長已經無法應用於過濾多個波長的特殊頻譜需求，因此進而促使一些多波長的元件譬如像高密度分波多工系統(DWDM)的問世。但此類元件多半利用兩個或兩個以上的獨立濾波器去達到其工作需求，在後續的元件積體化整合上將會變得更加困難，但如果使用相移式(phase-shift)長週期光柵去達到兩個甚至以上的抑制頻帶則可滿足此需求。
在本論文中，我們利用二次質子交換(two-step proton-exchange)技術成功地在LiNbO3基板上製作出可靠度高且造價低廉的長週期波導光柵元件，其光柵週期為Λ=44 μm。第一次質子交換主要是製作平面波導披覆層，其溫度控制在250°C，時間為4個小時，熱退火溫度為400°C，時間為70分鐘，而第二次質子交換法主要是製作波導層，其溫度控制在250°C，時間為55分鐘，而光柵製作則是利用AZ-5214E光阻，經由標準的黃光微影製作而成。後續的量測結果顯示此光柵元件光波長抑制對比度(dip contrast)最大可達到18dB，半高全寬(FWHM)約為2.8nm，共振波長為1549.5nm，其模擬與實驗結果都相符合。
接著利用相移長週期光柵理論設計出2、3、4、5等4種不同區段(section)的相位移長週期光柵，而隨著區段數M的增加，其兩個主要抑制頻帶之間的旁瓣(sidelobes)數為M-2，而低谷跨距(trough span)隨著區段數的增加則呈現線性的增加。

Long period fiber grating (LPFG) has been extensively researched and used in fiber optic communications systems, but its device applicability cannot be expanded any further due to the inherent limitations associated with the fiber such as its fixed cylindrical shape and optically linear dielectrics. In order to mitigate the fiber-entailed limitations and also to take into account for the monolithic integratibility of devices, long period gratings based on the various waveguide structures or sometime being collectively referred to as long period waveguide gratings (LPWGs) are therefore proposed. However, with the advent of integrated optical circuits, the traditional gratings functioned as filters only involve with a single wavelength, so for other device applications that involve the filtering and transmitting of multiple wavelengths such as the dense wavelength-division multiplexing (DWDM), the traditional LPWGs could hardly be proven useful! Therefore it would be wise if the LPWGs could be further improved in order to adapt to the foregoing demand. With this spirit in mind the concept of phase-shifted long-period gratings are hereby proposed, designed and fabricated in order to deliver the selective filter spectra that involve at least two rejection bands.
In this thesis, highly reliable and low cost long-period waveguide gratings in LiNbO3 substrates were successfully produced using the two-step proton-exchange (PE) process. The proton source needed for the experiment was supplied by stearic acid and the grating pitch (Λ) so designed was set at 44 μm. In the first PE process, the slab waveguide cladding was formed while the temperature was controlled at 250°C for 4-hour and annealed later at 400°C for 70 min. The second step PE process was executed to form the core while the temperature was set at 250°C for 55min. The grating pitch was produced using AZ5214-E photoresist via a standard photolithographic technique. The subsequent measurements showed that the maximum dip contrast of the LPG device was about 18dB and the full width at half maximum (FWHM) was about 2.8nm. The resonant wavelength was measured to be 1549.5nm, which agreed rather well with the simulation conducted beforehand.
The phase-shifted long period gratings with a finite number (M) of sections cascaded together are proposed and fabricated. It was expected theoretically and later justified experimentally that an M-section phase-shifted long period grating would produce (M-2) sidelobes between two dominant rejection bands, and the separation between the two rejection bands increased linearly with respect to M.

目錄

中文摘要 І
英文摘要 ІII
致謝 VI
目錄 VІII
表目錄 XI
圖目錄 XI

第一章 序論 1
1.1 光通訊簡介 1
1.2 光學積體電路 4
1.3 論文架構 6
參考文獻 7
第二章 長週期光柵 8
2.1 導論 8
2.2 長週期光纖光柵(Long-period fiber grating, LPFG) 9
2.3 長週期波導光柵(Long-period waveguide grating) 11
2.4 相位移長週期光纖光柵 15
參考文獻 20
第三章 LiNbO3光波導 25
3.1 導論 25
3.2 質子交換製作光波導 26
3.2.1 熱退火式質子交換(APE) 29
3.3 常用之非線性光學材料 32
3.4 金屬擴散式波導 33
參考文獻 35
第四章 波導光學特性與量測 38
4.1 導論 38
4.2 光波導的耦合效益 39
4.2.1 菱鏡耦合技術 39
4.2.2 邊射耦合技術(end fire coupling) 42
4.3 折射率分佈 45
4.4 光波導損耗來源及量測 46
4.4.1 損耗的來源 46
4.4.2 損耗之量測方法 48
參考文獻 49
第五章 長週期以及長週期相位移光柵之模擬設計與實驗 51
5.1 導論 51
5.2 結構模擬及設計 51
5.2.1 波導層與批覆層之模態有效折射率 53
5.3 元件製作流程 55
5.3.1 基板清洗 57
5.3.2 質子交換光波導 58
5.3.3 光阻光柵定義於波導 59
5.3.4 拋光以及研磨 62
5.3.5 光場量測 64
5.4 穿透頻譜(Transmission spectrum)量測分析 67
5.5 長週期光柵之頻譜分析 69
5.5.1 相位移長週期光柵之頻譜分析 70
5.5.2 相位移長週期光柵之頻譜模擬 71
5.5.3 兩個區段的相位移長週期光柵 74
5.5.4 三個區段的相位移長週期光柵 76
5.5.5 四個區段的相位移長週期光柵 78
5.5.6 五個區段的相位移長週期光柵 80
5.6 結論 82
參考文獻 85
第六章 結論與未來進展 86
6.1 結論 86
6.2 未來進展 88
參考文獻 89

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