Adibi, Ali

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    Hybrid Material and Device Platforms for Reconfigurable Integrated Nanophotonics
    (Georgia Institute of Technology, 2018-11-27) Adibi, Ali
    The development of ultra-compact integrated nanophotonic structures for communications, sensing, and signal processing has been of great interest lately. Recent progress in the development of miniaturized high-Q microresonators has resulted in orders of magnitude reduction in the size of functional integrated photonic structures. The possibility of low-power tuning of the resonance features in these structures has made the formation of reconfigurable photonic structures possible. Among existing CMOS-compatible substrates, silicon (Si) and silicon nitride (SiN) have been used the most. Despite impressive progress in Si-based and SiN-based integrated photonics, neither substrate alone can be used for practical applications. Si (despite its good reconfigurability) suffers from strong nonlinear effects (especially at high light intensities) and relatively large free-carrier loss while SiN (with one order of magnitude lower loss and lower nonlinearity compared to Si) is very hard to tune. Thus, a reliable material system that combines ultra-loss-loss and high power handling with efficient and fast reconfigurability is of high demand in integrated nanophotonics. In this talk, the recent achievements in the development and optimization of hybrid multi-layer CMOS-compatible material systems (e.g., SiN/Si, multi-layer Si/SiO2, etc.) to address all the practical requirements of ultra-fast and ultra-compact integrated photonic structures will be discussed. Using these hybrid material systems, a series of ultra-compact and high-performance reconfigurable photonic devices and subsystems that are formed by using high Q resonators will be demonstrated. The use of these devices and subsystems for realization of densely-integrated reconfigurable photonic chips for signal processing and sensing applications will be discussed.
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    Novel Silicon Nanophotonic Structures for Ultra-compact Integrated Lab-on-a-chip Sensing
    (Georgia Institute of Technology, 2008-03-11) Adibi, Ali
    The development of ultra-compact and sensitive sensing structures with minimal sample requirement for accurate sensing have been of great recent interest for multiple applications including bio and environmental sensing, chemical agent detection, and bio- threat detection. With recent advancement in the development of design and fabrication tools for photonic nanostructures, integrated photonic platforms are a strong candidate for the development of such sensing structures. In this talk, Prof. Ali Adibi first presented the requirements for the development of photonic lab-on-a-chip sensing structures. Then he explained how these requirements are met by two recent developments in our group in the area of silicon photonics, i.e., ultra-high Q micro-resonators, and ultra-compact photonic crystal on-chip spectrometers with orders of magnitude smaller size compared to the other implementations with the same performance. These spectrometers are enabled by dispersion engineering in photonic crystal to simultaneously achieve the superprism effect, negative diffraction, and negative refraction. Details of the design of such structures along with their experimental demonstrations will be presented.