本論文研究主要探討次波長光柵耦合器如何在入射光垂直入射耦合的情況下，降低穿透至基板的繞射光並維持高效率耦合，本研究所使用的模擬方法為有限時域差分法(Finite-Difference Time-Domain ; FDTD)，對於光柵週期、薄膜厚度、不同光柵結構、反射光柵的加入與布拉格反射鏡影響耦合效率做詳細的探討。 模擬上光源的為中心波長為1310 nm的高斯光束，波導材料選用為〖Ta〗_2 O_5，包覆層材料為〖SiO〗_2。模擬結果顯示結合布拉格反射鏡與反射光柵下最佳垂直耦合效率。並發現光柵週期的倍數亦可將光耦入波導。 製程上以電子束微影(Electron-beam lithography)製作光阻光柵於波導層上，並選用直接於光阻光柵上鍍製一層〖Ta〗_2 O_5包覆之製作耦合光柵，為一種可使光柵形貌與蝕刻製程相近之製程。 最後量測上，在利用單模光纖作為光源，強度為20mW的情況下，成功的將波長1310 nm的紅外光耦合進波導並耦合出，並量測到耦出光強為約35.3μW。 ;The purpose in this study is the design and fabrication of a sub-wavelength grating coupler with high efficiency for vertical coupling.We designed the coupler using the Finite-Difference Time-Domain (FDTD) method. The grating period, film thickness, different grating structure, reflector grating and distributed Bragg reflector were discussed to enhance the coupling efficiency in detail. The light source is a Gaussian beam with the central wavelength, 1310 nm. The waveguide layer and cladding layer materials are 〖Ta〗_2 O_5 and 〖SiO〗_2, respectively. The highest coupling efficiency 63% with reflector grating and distributed bragg reflector at wavelength 1310 nm was achieved by our simulation. The multiple grating period also has a high coupling efficiency. In experimental, we used electron-beam lithography to fabricate the sub-wavelength photoresist grating on a 〖Ta〗_2 O_5 waveguide layer. Then a 〖Ta〗_2 O_5 layer was deposited on the photoresist grating to form the coupler grating. Finally, a single-mode fibers light source with the intensity of 20mW was used to measure the sub-wavelength grating. The intensity of the out coupling light on the coupler grating is 35.3μW .
