High Clockrate Free-space Optical In-Memory Computing

Yuanhao Liang; James Wang; Kaiwen Xue; Xinyi Ren; Ran Yin; Shaoyuan Ou; Lian Zhou; Yuan Li; Tobias Heuser; Niels Heermeier; Ian Christen; James A. Lott; Stephan Reitzenstein; Mengjie Yu; Zaijun Chen

arXiv · 2509.19642

High Clockrate Free-space Optical In-Memory Computing

Yuanhao Liang·James Wang·Kaiwen Xue·Xinyi Ren·Ran Yin·Shaoyuan Ou·Lian Zhou·Yuan Li·Tobias Heuser·Niels Heermeier·Ian Christen·James A. Lott·Stephan Reitzenstein·Mengjie Yu·Zaijun Chen

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Abstract

The ability to process and act on data in real time is increasingly critical for applications ranging from autonomous vehicles, three-dimensional environmental sensing and remote robotics. However, the deployment of deep neural networks (DNNs) in edge devices is hindered by the lack of energy-efficient scalable computing hardware. Here, we introduce a fanout spatial time-of-flight optical neural network (FAST-ONN) that calculates billions of convolutions per second with ultralow latency and power consumption. This is enabled by the combination of high-speed dense arrays of vertical-cavity surface-emitting lasers (VCSELs) for input modulation with spatial light modulators of high pixel counts for in-memory weighting. In a three-dimensional optical system, parallel differential readout allows signed weight values accurate inference in a single shot. The performance is benchmarked with feature extraction in You-Only-Look-Once (YOLO) for convolution at 100 million frames per second (MFPS), and in-system backward propagation training with photonic reprogrammability. The VCSEL transmitters are implementable in any free-space optical computing systems to improve the clockrate to over gigahertz. The high scalability in device counts and channel parallelism enables a new avenue to scale up free space computing hardware.

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Yuanhao Liang, James Wang, Kaiwen Xue, Xinyi Ren, Ran Yin, Shaoyuan Ou, Lian Zhou, Yuan Li, Tobias Heuser, Niels Heermeier, Ian Christen, James A. Lott, Stephan Reitzenstein, Mengjie Yu, Zaijun Chen. 2025-09-23. High Clockrate Free-space Optical In-Memory Computing. https://arxiv.org/abs/2509.19642

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