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Open Access Publications from the University of California

Scholarly Works (3 results)

  • Thesis
  • Peer Reviewed
UC Santa Barbara Electronic Theses and Dissertations (2024)

This dissertation presents a path toward silicon photonic short reach dense wave-length division multiplexing interconnects capable of scaling to 1 Tbps with link energy consumption approaching 200 fJ/bit and areal densities exceeding 5 Tbps/mm2 within ambient operating temperatures ranging from 20 to 80 °C. The system’s architecture in the electronic and photonic domains, along with its evolution, are outlined with an em- phasis on the photonic aspects. Such a transceiver photonic integrated circuit contains hundreds of photonic elements that have stringent performance requirements with regards to footprint, energy consumption, and fabrication reproducibility, among other things. As such, the measured performance of many of these photonic elements is detailed; fur- ther, methods are shown for modelling the performance of some of these components for practical design, namely elements formed using Mach-Zehnder interferometers and microring resonators.

Forming a system of that is appropriately electrically and optically interconnected toperform requires extensive packaging, which is outlined in this work with a focus on the silicon photonics chip. Co-packaging validation experiments are shown, building towards a demonstration of a discrete silicon photonic transceiver and a packaged mode-locked laser comb source at 27 Gbps per wavelength.

Finally, to further the goal of quantifying fabrication uncertainties and their impacton silicon photonic systems, this work also introduces an experimental methodology to estimate the lithographic overlay error between a waveguiding layer and another layer capable of perturbing the guided mode; steps capable of introducing perturbations include ion implantation, etching of the waveguide layer, and deposition of material layers within close proximity to the waveguide. Such a tool should allow for more precise uncertainty quantification in photonic elements such as modulators, photodiodes, and passive mode- evolution based devices, which should in turn lead to more optimized component designs.

    • Article
    • Peer Reviewed
    UC Santa Barbara Previously Published Works (2023)
    Frequency-modulated (FM) laser combs, which offer a quasi-continuous-wave output and a flat-topped optical spectrum, are emerging as a promising solution for wavelength-division multiplexing applications, precision metrology, and ultrafast optical ranging. The generation of FM combs relies on spatial hole burning, group velocity dispersion, Kerr nonlinearity, and four-wave mixing (FWM). While FM combs have been widely observed in quantum cascade Fabry-Perot (FP) lasers, the requirement for a low-dispersion FP cavity can be a challenge in platforms where the waveguide dispersion is mainly determined by the material. Here we report a 60 GHz quantum-dot (QD) mode-locked laser in which both the amplitude-modulated (AM) and the FM comb can be generated independently. The high FWM efficiency of -5 dB allows the QD laser to generate FM comb efficiently. We also demonstrate that the Kerr nonlinearity can be practically engineered to improve the FM comb bandwidth without the need for GVD engineering. The maximum 3-dB bandwidth that our QD platform can deliver is as large as 2.2 THz. This study gives novel insights into the improvement of FM combs and paves the way for small-footprint, electrically pumped, and energy-efficient frequency combs for silicon photonic integrated circuits (PICs).
      Cover page: Broadband quantum-dot frequency-modulated comb laser.
      • Article
      • Peer Reviewed
      UC Santa Barbara Previously Published Works (2022)
      Microcombs have sparked a surge of applications over the past decade, ranging from optical communications to metrology1-4. Despite their diverse deployment, most microcomb-based systems rely on a large amount of bulky elements and equipment to fulfil their desired functions, which is complicated, expensive and power consuming. By contrast, foundry-based silicon photonics (SiPh) has had remarkable success in providing versatile functionality in a scalable and low-cost manner5-7, but its available chip-based light sources lack the capacity for parallelization, which limits the scope of SiPh applications. Here we combine these two technologies by using a power-efficient and operationally simple aluminium-gallium-arsenide-on-insulator microcomb source to drive complementary metal-oxide-semiconductor SiPh engines. We present two important chip-scale photonic systems for optical data transmission and microwave photonics, respectively. A microcomb-based integrated photonic data link is demonstrated, based on a pulse-amplitude four-level modulation scheme with a two-terabit-per-second aggregate rate, and a highly reconfigurable microwave photonic filter with a high level of integration is constructed using a time-stretch approach. Such synergy of a microcomb and SiPh integrated components is an essential step towards the next generation of fully integrated photonic systems.
        Cover page: Microcomb-driven silicon photonic systems
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