Design and Characterization of Optical Fiber-To-Chip Edge Couplers and On-Chip Mode Division Multiplexing Devices
Integrated silicon photonics has recently emerged as a promising solution to data interconnection in large data centers, which are characterized by short-range (0.5 – 2 km) and high bandwidth, i.e. 400 Giga-bit-per-second. Light from an external laser is first coupled to a silicon photonic chip, splits and modulated to carry data, and then multiplexed and coupled out to one or more optical fibers to take advantage of their large data bandwidth over their electric counterparts. However, short-range optical communication is still faced with several technical challenges. First, the difficulty to couple light between optical fibers and chips leads directly to significant power loss which reduces the transmission range. Therefore, a reliable scheme for fiber-to-chip coupling with high efficiency becomes imperative. Here we experimentally demonstrated various types of fiber-to-chip edge couplers and the best design yielded 0.56 dB/facet coupling loss for transverse-electric (TE) mode and 0.88 dB/facet for transverse magnetic (TM) modes, over a 100 nm bandwidth using lensed fiber. Additional challenges include (but not limit to) various on-chip optical multiplexing techniques. This thesis focuses on an emerging technique called mode division multiplexing (MDM), and presents designs, and in some cases experimental characterizations, for mode filtering, sharp bends, mode conversion as well as 3dB splitters. Polarization handling and wavelength selective routing are also vital parts of photonic transceivers. Some theoretical solutions for better polarization and wavelength handling will be presented. Recently, integrated photonics has also shown potential in emission and ranging applications for autonomous driving, robots, and intelligent production lines. I will present the far-field emission and beam steering based on integrated optical phase arrays. Several important aspects of optical phase array are investigated, including beam forming and channel crosstalk suppression.
Qi, Purdue University.
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