OptiLookUp: An Optical ROM-Based Loop up Table Engine for Photonic Accelerators

2026-05-04

AI Summary

This work addresses the lack of high-bandwidth, low-latency, and reconfigurable read-only memory (ROM) solutions in conventional photonic accelerators, which hinders efficient implementation of predefined nonlinear mappings such as activation functions. The authors propose an integrated microring resonator–based optical ROM architecture that directly encodes input–output mappings into the spectral response of the device. A photonic decoding mechanism enables selective addressing of tiled subarrays, facilitating deterministic lookup operations without dynamic computation. Reconfigurability is achieved through transistor-driven optical gating, eliminating the need for physical rewiring or interferometric structures. A tiled design mitigates cumulative insertion loss and enhances scalability. Device-level simulations on the GlobalFoundries 45SPCLO silicon photonics platform demonstrate a data rate of 12.5 GHz with stable optoelectronic conversion, successfully supporting nonlinear activation functions including Sigmoid, tanh, ReLU, and exponential.

Abstract

Read-only memory (ROM) provides deterministic access to predefined data mappings. Extending ROM concepts to the optical domain enables high-bandwidth, low-latency, and parallel memory access, but realizing compact and reconfigurable optical ROM remains challenging due to loss, wavelength control, and integration constraints. This work presents a high-speed, reconfigurable photonic ROM architecture implemented using integrated microring resonators (MRRs). The ROM encodes predefined input-output mappings directly in the spectral response of the photonic devices, enabling deterministic lookup-based operation without dynamic computation during readout. To improve scalability and reduce cumulative insertion loss, the architecture employs compact banked sub-arrays that are selectively addressed through an optical decoding mechanism. Reconfigurability is achieved using transistor-based optical selectors, allowing different ROM banks to be activated without physical light rerouting or interferometric structures. The proposed photonic ROM is designed and evaluated using device-level simulations based on the GlobalFoundries 45SPCLO silicon photonics platform. Simulation results demonstrate reliable operation at data rates up to 12.5 GHz, with stable light-to-current transfer characteristics obtained through integrated photodiode readout. The optical ROM can be used to implement nonlinear activation functions utilised in photonic accelerator architectures, including sigmoid, tanh, ReLU, and exponential mappings.

Problem

• optical ROM
• photonic accelerators
• lookup table
• reconfigurable photonics
• microring resonators

Innovation

• photonic ROM
• microring resonators
• optical lookup table
• reconfigurable photonics
• silicon photonics