| 摘要: | 光達(Lidar)技術的發展在近年中由於自駕車和智慧型無人載具等相關應用的興起變得非常蓬勃。目前世界上的主流車廠、和無數的新創公司, 無不全力以赴的將Lidar商品化。現在大部分已經商品化的Lidar是使用905 nm波段的光脈衝，機械旋轉鏡、並加上時域飛行的技術來實現。然而此種技術在多車同時啟動光達時仍有eye-safe的問題。而且整個模組的體積龐大。為了克服上述問題，在此計畫中，我們將展示一種利用連續波光波長調變(FMCW)技術的Lidar系統和其新穎的核心晶片(光引擎)。在此Lidar中我們會把中心波長推到1550 nm附近，此波長不但可以避免視網膜的吸收也可以使用相對成熟的光通信元件來實現光子積體迴路以利於Lidar系統微型化的終極目的。然而PIC最大的問題是在於是在於光子在輸入和輸出晶片時會蒙受巨大的損失(~ 10dB)，這對需要長距離(>100公尺)偵測的車用Lidar來說是完全無法接受的。我們在此計畫中將會把所開發的三五族的PIC光引擎(雷射和相移器陣列單晶整合)和主動式液晶透鏡做混成結合，以期把大部分的高損耗元件捨棄並實現2-D2-D掃描和3-D成像。 ;In the recent years, the development of Lidar technologies is booming due to its fancy applications in self-driving cars and unmanned vehicles. Now, lots of major car manufactures, big IT companies, and numerous star-up companies are dedicated to this topic. Up to now, most of the commercial available Lidar system is based on optical pulse at 905 nm wavelength, mechanical steering mirror, single-photon avalanche photodiode, and time-of-flight (ToF) technology. However, this kind of technology suffers the eye-safe issue when lots of cars are running Lidar system simultaneously. In addition, the size of this kind of Lidar module is usually bulky. In order to overcome the above-mentioned problems, we will demonstrate a frequency-modulated continuous-wave (FMCW) Lidar system and its novel core chip (optical engine) inside. In this FMCW lidar, we will push the operating wavelengths to around 1.55 m. Such optical window at telecommunication wavelengths can minimize the absorption in the retinal of people and we can realize our Lidar system based on the InP based photonic integrated circuit (PIC) technology, which is well-developed for the fiber communication industry. In addition, the PIC scheme can help us downscale the size of Lidar system. However, the major problems in the nowadays PIC is its huge Input/Output coupling loss (~10 dB) with outside environment. This is not acceptable for the self-driving car Lidar, which needs a capability in long range detection (>100 meter). In this project, we will have a hybrid integration for PIC, which is composed by DFB laser and phase-shifter array, with liquid crystal active lens. Based on such scheme, we can discard most of the lossy components in our PIC and realize 2-D scanning and 3-D imaging. Besides, we will demonstrate a novel avalanche photodiode (APD) array, which can provide high responsivity and high saturation current in the receiver end. By use of such gadget, an improved signal-to-noise (S/N) ratio and longer ranging distance can be expected. |
