本論文使用stimulated Raman adiabatic passage (STIRAP)的概念設計出非對稱絕熱耦合器的結構，並且將此結構應用在鈦擴散式鈮酸鋰波導上，作為偏振分光器。而此設計是用兩段的結構，將兩個不同的偏振光分開，已達成偏振分光器的效果。在模擬上，先針對不同結構的情況去比較，以1550 nm為中心波長，使TE、TM偏振都能達到良好的效果，再將結果結合，進行大範圍波長的模擬，來達成寬頻分光器的效果，最後在對pump的偏振光進行模擬，以波長775 nm為主，兩個偏振的pump光只會從C出口輸出。而本論文利用模擬結果的結構，實際製作出寬頻偏振分光器的晶片，並加以量測。 在本實驗的製程是以黃光微影以及高溫擴散的方式，製作出鈦擴散式鈮酸鋰波導非對稱絕熱耦合器之寬頻偏振分光器，最後進行兩個端面的拋光，來完成晶片的製作。 在量測的結果上，在波長範圍1500 nm到1600 nm，兩個偏振都有良好的分光比，大約在95%到99%之間，TM偏振的寬度在120 nm，TE偏振的寬度在130 nm，都有著很寬的範圍。 ;In this study, the structure of asymmetric adiabatic coupler (AAC) is designed using the concept of Stimulated Raman Adiabatic Passage (STIRAP), and applied it on the lithium niobate(LiNbO3) with the titanium diffused waveguides to become a polarization beam splitter. We designed the structure into two parts to split TE and TM polarization. Our goal is to achieve the broadband polarization beam splitter by using a two-stage structure to separate two different polarized lights. Before the fabrication process, we do the simulation part. In the simulation process, first step we use 1550 nm as the center wavelength to simulate TE and TM polarization in different structures. Second step, based on our previous simulation, we apply an adiabaticity engineering method to optimize the waveguide system configuration to achieve a broadband polarization beam splitter. Finally, we use a TE-polarized 775 nm laser as the pump to examine the structure to make sure the pump will be spatially filtered from the cross-polarized signal and idler. Furthermore, we fabricated such an AAC chip to measure the experimental result. We used the standard lithography process and titanium diffusion process to fabricate the AAC chip in a 51 mm long, 25 mm wide, and 0.5 mm thick LiNbO3 crystal. In the measurement result, we had a good-fitting result with the simulation process. It can be found a bandwidth of >120 nm can be achieved in this unique Ti:LiNbO3 polarization beam splitter at a power splitting ratio of >95% for both polarization modes, which is to the best of our knowledge the broadest bandwidth ever reported in integrated optical LiNbO3 polarization beam splitters.
