Browsing by Author "Uddin, S. M. Zia"
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Item Metasurface on integrated photonic platform: from mode converters to machine learning(Nanophotonics, 2022-07-20) Wang, Zi; Xiao, Yahui; Liao, Kun; Li, Tiantian; Song, Hao; Chen, Haoshuo; Uddin, S. M. Zia; Mao, Dun; Wang, Feifan; Zhou, Zhiping; Yuan, Bo; Jiang, Wei; Fontaine, Nicolas K.; Agrawal, Amit; Willner, Alan E.; Hu, Xiaoyong; Gu, TingyiIntegrated photonic circuits are created as a stable and small form factor analogue of fiber-based optical systems, from wavelength-division multiplication transceivers to more recent mode-division multiplexing components. Silicon nanowire waveguides guide the light in a way that single and few mode fibers define the direction of signal flow. Beyond communication tasks, on-chip cascaded interferometers and photonic meshes are also sought for optical computing and advanced signal processing technology. Here we review an alternative way of defining the light flow in the integrated photonic platform, using arrays of subwavelength meta-atoms or metalines for guiding the diffraction and interference of light. The integrated metasurface system mimics free-space optics, where on-chip analogues of basic optical components are developed with foundry compatible geometry, such as low-loss lens, spatial-light modulator, and other wavefront shapers. We discuss the role of metasurface in integrated photonic signal processing systems, introduce the design principles of such metasurface systems for low loss compact mode conversion, mathematical operation, diffractive optical systems for hyperspectral imaging, and tuning schemes of metasurface systems. Then we perceive reconfigurability schemes for metasurface framework, toward optical neural networks and analog photonic accelerators.Item Micro-dispenser-based optical packaging scheme for grating couplers(Optics Letters, 2023-04-13) Uddin, S. M. Zia; Gupta, Ellen; Rahim, Masudur; Wang, Zi; Du, Yang; Ullah, Kaleem; Arnold, Craig B.; Mirotznik, Mark; Gu, TingyiDue to their sub-millimeter spatial resolution, ink-based additive manufacturing tools are typically considered less attractive than nanophotonics. Among these tools, precision micro-dispensers with sub-nanoliter volumetric control offer the finest spatial resolution: down to 50 µm. Within a sub-second, a flawless, surface-tension-driven spherical shape of the dielectric dot is formed as a self-assembled µlens. When combined with dispersive nanophotonic structures defined on a silicon-on-insulator substrate, we show that the dispensed dielectric µlenses [numerical aperture (NA) = 0.36] engineer the angular field distribution of vertically coupled nanostructures. The µlenses improve the angular tolerance for the input and reduces the angular spread of the output beam in the far field. The micro-dispenser is fast, scalable, and back-end-of-line compatible, allowing geometric-offset-caused efficiency reductions and center wavelength drift to be easily fixed. The design concept is experimentally verified by comparing several exemplary grating couplers with and without a µlens on top. A difference of less than 1 dB between incident angles of 7° and 14° is observed in the index-matched µlens, while the reference grating coupler shows around 5 dB contrast.