長週期光柵(Long-period grating, LPG)形成於單模光纖或波導，其研究著重在基本波導模態(fundamental guided mode)和批覆層模態(cladding mode)之間的耦合特性，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，然而，利用光纖來做長週期光柵會有幾何形狀和材料選擇上的限制，尤其是在主動元件上的實現。所以，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。
在本論文中，使用Ag+-Na+離子交換技術成功的製作出可靠度高且造價低廉的積體光波導元件，並將其製作在矽酸鹽玻璃基板N-BK7，而交換混合熔鹽的來源為AgNO3:NaNO3 (mole ratio ~0.04:1)且溫度控制在340°C，而交換時間為3個小時，其折射率變化可達Δn~0.03。其批覆層的材料則是利用電漿輔助式化學氣相沉基法(PECVD)，藉由控制SiH4、NH3、N2O與N2等氣體反應之流量，於玻璃基板上沉積出一系列的氮氧化矽(SiON)薄膜，此不同氮/氧比例之SiON薄膜，其有效折射率的分佈範圍可從1.47至1.94。
我們利用模擬軟體設計四種不同光柵週期之元件，分別為Λ=141 μm、Λ=161 μm、Λ=171 μm和Λ=191 μm，其中當光柵間距為141μm時，其對比度(Contrast)最大可達20 dB，半高全寬(FWHM)約為3.5 nm，而模擬與實驗結果相符合。

Long-period fiber gratings (LPFGs) are functioned based on the light coupling between the core guiding modes and the cladding modes in the single-mode fiber at specific wavelengths (resonance wavelengths), which have found a wide variety of applications in the optical communications. However, using geometry and material constraints associated with the fiber impose significant limitations on the functionalities of the devices could offer, notably for the cases involving active devices. To bypass the foregoing constraints, the waveguide with long-period waveguide gratings (LPG) are thus developed so that the flexibility in designing various LPG-based devices can be realized.
In this thesis, LPWG are fabricated by the wet ion-exchange using AgNO3:NaNO3 molten salt with the mole ratio of 0.04 to 1 maintained at the temperature of 340°C. The oxynitride based cladding layer is deposited using plasma-enhanced chemical vapor deposition (PECVD) by judiciously controlling the flow rates of SiH4, NH3, N2O and N2, in such a way that SiON films with different nitrogen and oxygen ratios can be deposited, with the corresponding effective refractive indices varied from 1.47 to 1.94.
As from the design perspective simulation software is used to design gratings with four different pitches, namely, Λ = 141 μm, Λ = 161 μm, Λ = 171 μm and Λ = 191 μm. The fabricated devices ultimately demonstrate a contrast of up to 20 dB and full width at half maximum (FWHM) of about 3.5 nm. Our results show that there is a reasonable agreement between the simulation and experimental results.

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