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Flat optics has been recently unveiled as a powerful platform to perform data processing in real-time, and with small footprint [1, 2, 3]. So far, these explorations have been limited to linear optics, while arguably the most impactful operations stem from nonlinear processing of the incoming signals. In this context, here we add a new twist and depth to analog optical computing: we demonstrate that nonlinear phenomena combined with engineered nonlocality in flat-optics devices can be leveraged to synthesize Volterra kernels able to perform complex operations on incoming images in real-time.
Metasurfaces have already introduced a paradigm shift for nonlinear optics enabling stronger nonlinearities in thin films and manipulation of the nonlinearly-generated wavefront [4, 5, 6]. In this framework, here we show that it is possible to exploit nonlocal nonlinearities as a powerful tool for analog computing with light waves. We show that using nonlinear nonlocality in flat optics we can realize analog image processing with previously not accessible functionalities. By exploring the simple scenario of a uniform χ2 thin sheet, we demonstrate edge detection operation with exciting potentials. In our proposed nonlinear flat-optics solution, the non-resonant nature of the nonlinear interaction involved in image processing allows edge detection over a broadband spectrum with ultra–high contrast and superior resilience to noise.
Our results indicate that Volterra kernels of nonlinear nonlocal flat optics can open new opportunities in applications such as image processing, item recognition for computer vision, and high-contrast, high-resolution microscopy.
References
1. Solli, D.R., Jalali, B., Nature Photonics 9(11), 704–706 (2015).
2. Silva, A., Monticone, F., Castaldi, G., Galdi, V., Alù, A., Engheta, N., Science 343(6167), 160–163 (2014).
3. Overvig, A., Alù, A., Laser & Photonics Reviews 16(8), 2100633 (2022).
4. Vabishchevich, P., Kivshar, Y., Photon. Res. 11, B50-B64 (2023)
5. Schlickriede, C., Waterman, N., Reineke, B., Georgi, P., Li, G., Zhang, S., Zentgraf, T., Advanced Materials 30(8), 1703843 (2018).
6. Gigli, C., Marino, G., Artioli, A., Rocco, D., De Angelis, C., Claudon, J., Gerard, J.-M., Leo, G., Optica 8(2), 269–276 (2021).
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