Browsing by Author "Mao, Dun"

Now showing 1 - 5 of 5
  • Thumbnail Image
    Item
    Active silicon photonics hybrid integration for high-speed applications and performance evaluation after cosmic environment
    (University of Delaware, 2023) Mao, Dun
    Silicon (Si) photonics offers great opportunities for on-chip optical interconnects, optical communications, signal processing, and sensing for its advantages of complementary metal-oxide semiconductor (CMOS)-compatibility, high yield, low power consumption, and high data rates. However, conventional Si photonics components may have bottlenecks due to the limited material property of silicon for high-speed, high efficient, and tunable operations. Also, the performance reliability of silicon devices under harsh (such as cosmic) environments is unknown. This thesis focuses on a few topics addressing those concerns. First, it evaluates the performance change of silicon Mach-Zehnder Modulators after cosmic radiation, laying a fundamental step for future deploying silicon based on chip optical communications in aerospace. Then, the hybrid integration of low-dimensional materials on silicon is demonstrated for high-speed optoelectronic devices and all-optical trimming devices. Last, direct laser writing technique is proposed to have direct patterning and material phase change on some thin film materials for low-cost and mask-free device patterning and tunable device applications.
  • Thumbnail Image
    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, Tingyi
    Integrated 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.
  • Thumbnail Image
    Item
    Photocatalytic Oxidation in Few-Layer Tellurene for Loss-Invariant Integrated Photonic Resonance Trimming
    (Advanced Optical Materials, 2023-05-05) Mao, Dun; Wang, Yixiu; Lee, Hwaseob; Chang, Lorry; Wang, Feifan; Wu, Darren; Xiao, Yahui; Sun, Boshu; Ullah, Kaleem; Booksh, Karl; Wu, Wenzhuo; Gu, Tingyi
    Two-dimensional (2D) materials with unique physicochemical properties promote photocatalytic activities. As the 2D material composites research studies the statistical average of complex catalytic behaviors, an integrated photonic platform allows for clean and single flake level photo-catalytic investigations with precisely quantified photocatalytic activities. In this paper, fluence-dependent photo-oxidation in two-dimensional Tellurene (2D Te) is tracked by the evanescently coupled micro-resonator. Nearly 32% of oxidation is achieved in ≈10 nm 2D Te flake, compared to only 4.5% oxidation in a 30 nm sample, probed by the resonance shift in silicon micro-ring resonators substrate. The wider bandgap in the few layers of 2D Te allows faster charge transfer to adsorbed oxygen for a more efficient photocatalytic redox reaction. The photo-oxidation in hybrid 2D Te results in invariant lineshapes of optical transmission resonance for wavelength trimming (more than 3× resonance bandwidth). The low threshold power, near-infrared, and in-waveguide resonance trimming scheme is compatible with most integrated photonic setups for easy fixing of the nanofabrication-induced random resonance deviation for integrated photonic circuit applications in wavelength-division-multiplexing systems and spin qubits quantum computing.
  • Thumbnail Image
    Item
    Silicon electro-optic modulators based on microscopic photonic structures: from principles to advanced modulation formats
    (Journal of Physics D: Applied Physics, 2023-08-04) Yu, Fuhao; Zeng, Zhaobang; Ji, Xiang; Tang, Kaifei; Xin, Yu; Wu, Guihan; Mao, Dun; Gu, Tingyi; Huang, Qingzhong; Jiang, Wei
    This paper reviews the progress of electro-optic modulators composed of silicon-based microscopic photonic structures. The basic principles, device structures, and advanced modulation capability of different geometric types are detailed for micro-ring modulators, photonic crystal modulators, and other related modulators. We illustrate the device operation mechanism with a focus on its photonic aspect and discuss their impacts on the modulator speed, power consumption, and thermal stabilities. The cavity enhancement and slow light effect significantly reduce the device footprint and power consumption, with the trade-off of limited operation wavelength range. Other emerging microscopic photonic structure-based silicon modulators for advanced modulation formats exhibit promising performance for further optimizations. Finally, we discuss the existing challenges and further directions of microscopic photonic structure-based silicon modulators for pertinent applications.
  • Thumbnail Image
    Item
    Structural Phase Transitions between Layered Indium Selenide for Integrated Photonic Memory
    (Advanced Materials, 2022-04-18) Li, Tiantian; Wang, Yong; Li, Wei; Mao, Dun; Benmore, Chris J.; Evangelista, Igor; Xing, Huadan; Li, Qiu; Wang, Feifan; Sivaraman, Ganesh; Janotti, Anderson; Law, Stephanie; Gu, Tingyi
    The primary mechanism of optical memoristive devices relies on phase transitions between amorphous and crystalline states. The slow or energy-hungry amorphous–crystalline transitions in optical phase-change materials are detrimental to the scalability and performance of devices. Leveraging an integrated photonic platform, nonvolatile and reversible switching between two layered structures of indium selenide (In2Se3) triggered by a single nanosecond pulse is demonstrated. The high-resolution pair distribution function reveals the detailed atomistic transition pathways between the layered structures. With interlayer “shear glide” and isosymmetric phase transition, switching between the α- and β-structural states contains low re-configurational entropy, allowing reversible switching between layered structures. Broadband refractive index contrast, optical transparency, and volumetric effect in the crystalline–crystalline phase transition are experimentally characterized in molecular-beam-epitaxy-grown thin films and compared to ab initio calculations. The nonlinear resonator transmission spectra measure of incremental linear loss rate of 3.3 GHz, introduced by a 1.5 µm-long In2Se3-covered layer, resulted from the combinations of material absorption and scattering.