在此篇論文中，利用擴散限制蝕刻技術，來蝕刻出垂直漸變式波導。我們以變化各種不同的間隙寬度以及遮罩寬度，可以得到不同的蝕刻速率，因此最後固定間隙寬度在20 μm，變化其遮罩寬度，可以得到線性，且最大相對蝕刻速率比值為2倍的特性，利用此種方式來製作漸變式波導。
由於要設計與傳統方式不同的光模轉換雷射，因此我們設計在上層SCH區域中製作垂直漸變式結構，而在考量了電流注入的情況，所以設計5層不同能隙波長的SCH結構，並利用模擬軟體將SCH的結構最佳化，而SCH的能隙波長以線性方式由1Q漸變式1.3Q 。
而後以半導體製程方式，使用擴散限制蝕刻的技術，將垂直漸變式結構製作於上層SCH之中，並且並已成功製作出具有垂直方向的漸變式波法布里-波羅雷射。其雷射臨限電流最小為17.5 mA，其最大功率為4.36 mW和阻值為21.3 Ω。
而此製作出來的半導體雷射其發散角在水平方向約為25.6°至28.5°，而在垂直方向上，法布理-波羅雷射發散角為41.2°，而垂直漸變式波導雷射則為30.3°，因此在使用垂直漸變式結構，使得光場散射角變小，而達到光模轉換之效果。

In this thesis, the diffusion-limited etching method is used to obtain a tapered waveguide structure with a gradual change in then vertical direction. We use different gap widths and mask widths to control the etching rate. Under optimal conditions, we can have a maximum etching selectivity ratio of 2. By this way, we can reshape the geometry of output light beam from ellipse to circle for improving the optical coupling between waveguide and optical fiber. To integrate such vertical spot-size converter with a conventional semiconductor laser, the epitaxial layers of the laser structure should be properly designed.
By taking current injection into account, the upper SCH layer is designed to be a five-layer structure, where the energy bandgap of the SCH is linearly changed from 1.0Q to 1.3Q. A 250 nm thick of upper SCH layer is used for fabricating the taper structure.
I have successfully realized the vertical-tapered FP lasers. Conventional FP-lasers are also fabricated as reference devices. Divergence angles for the output light beams from both type of lasers are about 25.6 degree to 28.5 degree in the horizontal direction. For the vertical direction, the vertical-tapered FP laser shows smaller divergence angles (30.3 degree) as compared to the conventional ones (41.2 degree). Therefore. It is believed that a vertical-tapered FP laser with smaller divergence angles can be realized by using diffusion-limited etching method.

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