BEIJING — In a major breakthrough for the field of optical computing, researchers from Peking University and Harbin Engineering University have successfully induced a beam of light to exhibit three stable states within a silicon photonic crystal microcavity. Measuring just 20 micrometers in diameter—thinner than a human hair—this ultra-compact hardware milestone marks a critical leap past the traditional constraints of binary “on” and “off” computing. By enabling a single storage unit to hold more information via optical tristability, the team has successfully built and demonstrated a prototype multi-valued optical memory device. Crucially, the system operates at an incredibly low switching power of just 240 microwatts, which consumes less energy than a standard commercial laser pointer.
Engineering multi-state light on micro- and nano-scale chips has historically been hindered by the exceptionally weak non-linear effects of light at such small scales. To overcome this barrier, the Chinese research team utilized a physics mechanism called “near-exceptional-point coupling,” designing two resonant modes inside the microcavity. When pushed toward an “exceptional point,” these modes tightly couple, causing their wavelengths to draw close and their linewidths to converge. This allowed the microcavity to achieve a quality factor of one million, confining the light so efficiently that it oscillates repeatedly before decaying. Published in Nature Nanotechnology, this breakthrough provides a foundational building block for the imminent scaling of optical neural networks and high-efficiency neuromorphic computing processors.
