Miniaturized III-Nitride Asymmetric Optical Link for the Monitoring of Vascular Heart Rate and Cardiac-Related Pulse Activity

Abstract

Multifunctioning InGaN/GaN multi-quantum well (MQW) diodes can transmit and detect light separately. In particular, MQW diodes have spectral overlap between electroluminescence (EL) and responsivity, conferring the unique ability to detect light emitted by another device sharing an identical MQW structure. Herein, a III-nitride transmitter and a receiver on a single chip are monolithically integrated, which can establish an asymmetric optical link and significantly reduce material and processing costs. By attaching the chip to the skin with the transmitter emitting toward it, the device can monitor cardiac activity. Heart pulses change blood volume of the vascular bed, which modulates the reflected light. The receiver absorbs that light and converts it into electrical signals. Finally, by integrating a programmed circuit, the biological signals are analyzed. Herein, a feasible approach to monitor heart rate and cardiac-related pulse information simultaneously is provided.