Three-dimensional laser micro/nano printing for optical computing

Abstract

With the rapid growth of data-intensive computing, optical computing has become an important method for information processing with high bandwidth, low latency, and parallel operation. Early implementations were bench-top free-space systems, in which lenses, masks, and holograms were used to perform Fourier filtering, correlation, and image processing. Semiconductor micro/nanofabrication has further enabled miniaturized planar platforms for optical computing, where optical-field manipulation is largely confined to planar geometries. However, increasing the integration density of optical computing architectures and exploiting the vectorial and spatial degrees of freedom of optical fields require additional out-of-plane structuring and direct integration on optical interfaces beyond planar fabrication. Three-dimensional (3D) laser micro/nano printing provides a maskless additive route to meet this need by directly printing freeform optical micro/nanostructures in 3D space and on functional optical interfaces. In this review, we discuss laser-printed structures for optical computing, including diffractive processors, interface-integrated processors, and 3D photonic interconnects. The printed processors map input optical fields to designed outputs, retrieve encoded information, or transform spatial modes, whereas the interconnects route optical signals between processing nodes. We further examine printable materials, printing resolution, and printing throughput in terms of the fabrication requirements of printed optical-computing structures. Finally, we discuss four future directions: reconfigurable modulation, nonlinear optical activation, freeform 3D optical layouts, and heterogeneous optical integration.