在現今探測距離技術中，使用LiDAR在對於機器人、無人自駕車等等都佔有一席之地。而傳統LiDAR是以光學與機械式部件作為光束的掃描，在不考慮LiDAR的高價位之情況，其在嚴峻的工作環境下，掃描速度、穩定性及體積小特性需要被顯著地提升，因此快速掃描與積體化的LiDAR是未來的發展方向。透過矽光子積體電路之技術將LiDAR微小化，且為了提升轉向角及減少熱控制器的數量，需將天線陣列之間的間距設計在半波長附近，並使用聯級熱相移器，使得可視場(Field of View)放大至接近180°左右，同時大幅減少熱控制器數量。但因天線陣列間距設計在半波長附近，導致波導非常密集，會衍生出串擾(Crosstalk)的問題，因此本論文將會深入的討論矽線波導與光學天線之間如何降低耦合及相位串擾對於波束成形遠場之影響。
為了減少一維與二維LiDAR過於複雜的熱控制器之數量，我們使用聯級熱移相器陣列。因為可視場之角度提升使得天線陣列間距非常密集，波導之間會有串擾的問題，所以欲降低一維波導天線陣列間的串擾，本論文設計了一維線寬變化的波導天線陣列。由於聯級熱相移器陣列為同時調制多根天線之相位，其無法直接調制因線寬變化而導致天線陣列間之相位差，因此我們額外加入錐形波導做相位補償。本論文最後將一維天線陣列的間距縮小，使LiDAR的可視場達到110°；二維低耦合天線陣列為使用矽帶光柵結構來降低傳統二維光學天線陣列之間的串擾，該串擾之降低幅度約為3-dB。其中二維光學天線陣列的間距為1μm，根據理論可得知，可視場在1μm的天線陣列間距下約為110°。

In modern detection and ranging technology, the light detection and ranging (LiDAR) systems are used in almost every robotics and autonomous vehicles. Free-space optics and mechanical components are typically utilized to steer the beam in LiDAR, which is unstable, bulky, expensive, and not suitable in a harsh environment. Moreover, the fabrication maturity in silicon photonic integrated circuit could miniaturize the photonic system. Thus, a high scan rate and solid-state LiDAR on silicon-on-insulator (SOI) platforms are becoming trends currently. To increase the output steering angle and reduce the controller number in an antenna array, the antenna spacing should be as close as the half operating wavelength. The cascade thermal phase shifter makes the field of view (FoV) to approximate 180° while the controller number is significantly reduced. However, if the antenna spacing is too close, the crosstalk between the antenna array will increase. In this thesis, it will be demonstrated to reduce the coupling influence and phase crosstalk between the optical antenna for far-field beamforming.
To reduce overly complicated heat controllers, a cascaded thermal phase shifter array is used. For horizontal steering, the antenna spacing is as close as half of the operating wavelength and shows the low crosstalk using index-mismatched waveguides and phase-compensation. Moreover, the same output optical waveguide mode needs to be further considered to demonstrate the grating lobe-free beam steering. And its FoV experimentally shows 110°.
For two-dimensional beam forming, the low coupling between antenna array consists of the close half-operating-wavelength spacing integrated with a silicon-strip-grating structure. Then the 8 channel array with a 1-μm pitch is simulated through finite difference time domain (FDTD) methods and shows a 3-dB reduction in array crosstalk and 5-dB improvement in grating lobe at a 30° steering angle.

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