Highly Scalable Synthesis of Mechanoluminescent Microspheres for Nanowatt‐Responsive Optocoupler Relays in Underwater Laser Communication

Low‐power optical input triggering high‐power optical output is a long‐sought capability in optoelectronic systems, as it holds the key to breaking the energy efficiency bottleneck of next‐generation isolated devices, optical switching, and power management modules. Here, we present a passive‐driven mechanoluminescent optocoupler relay (MLOCR) fabricated via pioneering a universal, highly scalable and size tunable preparation of mechanoluminescent microspheres (97 µm to 1.52 mm), which enables reliable galvanic isolation without electrical input, operating instead with nanowatt‐level optical emission. This device achieves an exceptional signal power ratio exceeding 6.4 × 10 8 ‐ a value six orders of magnitude higher than that of the commercial EL817 LED‐based OCR. Notably, the MLOCR exhibits ultrastable operation at 423 K and outperforming commercial baselines by fourfold (360 vs. 90 s). Finally, our MLOCR is applied to drive a 10 W high‐power laser by 15.59 nW optical input for underwater optical communication. This work has established a novel foundational paradigm for the integration of mechanoluminescence into zero‐power‐consumption optoelectronic devices.