All-optical physiological sensing and communication system on GaN

Multiple-quantum-well (MQW) diodes inherently exhibit both light-emitting and light-detecting capabilities due to the overlap between their emission and detection spectra. In this work, an integrated all-optical physiological sensing and communication system is demonstrated based on MQW diodes operating within the overlapping wavelength range of 438–483 nm. Local photoplethysmography signals are acquired via reflective optoelectronic interaction between the MQW diode and biological tissue and are directly modulated onto the emitted optical signal for transmission. The physiological information is delivered through a 30 cm free-space optical link and recovered by a structurally identical MQW diode at the receiver, establishing a seamless optical pathway from sensing to remote readout. This architecture enables fully optical physiological signal acquisition and transmission without reliance on radio frequency emission. The proposed system offers a promising solution for health monitoring in electromagnetically sensitive or restricted environments.