Low-coherence light enhances photonic computing

Now, writing in Nature, Dong, Brückerhoff-Plückelmann and colleagues demonstrate that low-coherence light can, somewhat counterintuitively, be employed for photonic convolutional computing, and even enhance it (B. Dong et al. Nature 632, 55–62; 2024).

The low-coherence light, produced by filtering the emission from an erbium-doped fibre amplifier, is evenly split by amplitude between N input channels, with each channel's amplitude modulated to form the N-element input vector (see picture). This input vector is then sent into a chip with weighting elements to perform matrix calculations. On the other hand, a coherent system requires wavelength multiplexing, demanding N separate optical bands to achieve the same N-element vector while avoiding unwanted interference. Thus, the incoherent approach increases parallelization, as N times more operations can be performed simultaneously within a single frequency band compared to a coherent system.