Browsing by Author "Shafiee, Amin, author"

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Open Access
Design space exploration for PCM-based photonic memory
(Colorado State University. Libraries, 2023-06-05) Shafiee, Amin, author; Charbonnier, Benoit, author; Pasricha, Sudeep, author; Nikdast, Mahdi, author; ACM, publisher
The integration of silicon photonics (SiPh) and phase change materials (PCMs) has created a unique opportunity to realize adaptable and reconfigurable photonic systems. In particular, the nonvolatile programmability in PCMs has made them a promising candidate for implementing optical memory systems. In this paper, we describe the design of an optical memory cell based on PCMs while exploring the design space of the cell in terms of PCM material choice (e.g., GST, GSST, Sb2Se3), cell bit capacity, latency, and power consumption. Leveraging this design-space exploration for the design of efficient optical memory cells, we present the design and implementation of an optical memory array and explore its scalability and power consumption when using different optical memory cells. We also identify performance bottlenecks that need to be alleviated to further scale optical memory arrays with competitive latency and energy consumption, compared to their electronic counterparts.
Open Access
GHOST: a graph neural network accelerator using silicon photonics
(Colorado State University. Libraries, 2023-09-09) Afifi, Salma, author; Sunny, Febin, author; Shafiee, Amin, author; Nikdast, Mahdi, author; Pasricha, Sudeep, author; ACM, publisher
Graph neural networks (GNNs) have emerged as a powerful approach for modelling and learning from graph-structured data. Multiple fields have since benefitted enormously from the capabilities of GNNs, such as recommendation systems, social network analysis, drug discovery, and robotics. However, accelerating and efficiently processing GNNs require a unique approach that goes beyond conventional artificial neural network accelerators, due to the substantial computational and memory requirements of GNNs. The slowdown of scaling in CMOS platforms also motivates a search for alternative implementation substrates. In this paper, we present GHOST, the first silicon-photonic hardware accelerator for GNNs. GHOST efficiently alleviates the costs associated with both vertex-centric and edge-centric operations. It implements separately the three main stages involved in running GNNs in the optical domain, allowing it to be used for the inference of various widely used GNN models and architectures, such as graph convolution networks and graph attention networks. Our simulation studies indicate that GHOST exhibits at least 10.2 × better throughput and 3.8 × better energy efficiency when compared to GPU, TPU, CPU and multiple state-of-the-art GNN hardware accelerators.
Open Access
Invited paper: Bridging EDA and silicon photonics design: enabling robust-by-design photonic integrated circuits
(Colorado State University. Libraries, 2025-03-04) Ghanaatian, Zahra, author; Mirza, Asif, author; Shafiee, Amin, author; Pasricha, Sudeep, author; Nikdast, Mahdi, author; ACM, publisher
Silicon photonic devices are essential components of integrated optical communication systems and emerging photonic processors. However, their performance is notably impacted by fabrication-process variations (FPVs), which primarily stem from optical lithography imperfections. The impact of FPVs can accumulate and deteriorate the system-level performance through, for example, increasing system power consumption, accumulated crosstalk noise, and degrading signal integrity in photonic systems. In this paper, we discuss the promise of variation-aware design-space exploration and optimization to enhance photonic device robustness under different FPVs while considering two silicon photonic devices used widely in different applications, namely Microring Resonators (MRRs) and Mach-Zehnder Interferometers (MZIs). In addition, we consider a system-level case study of an MZI-based coherent neural network, where we show how our proposed variation-aware design optimization at the device level helps improve the network accuracy by up to 88% under FPVs.