光纖光柵的製作與應用

Abstract

本文首先敘述我們製作低邊裙(side-lobes)光纖光柵的方法，包括使用均一性相位光罩(uniform phase mask)及非均一性相位光罩，來達到鐘形化(apodisation) 的效果。我們的製造原理在於適當調制曝製過程中背景光的分佈來得到大小相同的平均折射率分佈。製成的光纖光柵在反射率接近99.9%時，邊裙可小於-30dB，輻射模(radiation mode)的影響小於1dB，及半高寬(FWHM)僅約0.5nm。在本論文中我們也將光纖光柵應用於感測系統及半導體雷射之穩頻，包括將布拉格光纖光柵(Fiber Bragg Grating, FBG)的波長變化用長週期光纖光柵(Long Period Fiber Grating, LPG)來解調，以得到靈敏度高的光纖感測系統；及將光纖光柵作為半導體雷射的外腔，回授其相對應之中心波長，以得到旁模壓抑比(Side Mode Suppression Ratio, SMSR)高的雷射輸出。最後我們探討利用相位移光纖光柵來製作窄頻光纖雷射，以及使用光纖光柵來製作光塞取多工器等應用。

In the dissertation we study the fabrication of low side-lobe fiber Bragg gratings (FBGs) by using uniform and apodised phase masks to achieve their apodisation. Our methods are by controlling the distribution of the back ground light in the fabrication process so as to equalize the average index along the FBG. The band width of the fabricated FBG is about 0.5 nm, with the radiation loss less than 1dB, and the side lobe -30 dB smaller compared to the maximum reflectivity (99.9%) of the top band. We have also applied the FBG to the fiber sensing system as well as to the frequency stabilization of a diode laser. In the sensor application, we demodulate the wavelength shift of the FBG by a long period fiber grating (LPG) to achieve a sensor system with high sensitivity. We have also studied the applications of a wavelength feed-backed external cavity FBG diode laser to achieve a high side-mode suppression ratio (SMSR) laser. And we use a □-phase shift FBG to achieve a narrow line-width fiber laser, as well as use FBGs to build optical add-drop multiplexers.