Multiple-quantum well (MQW) III-nitride diodes can both emit and detect light. In particular, a III-nitride diode can absorb shorter-wavelength photons generated from another III-nitride diode that shares an identical MQW structure because of the spectral overlap between the emission and detection spectra of the III-nitride diode, which establishes a wireless visible light communication system using two identical III-nitride diodes. Moreover, a wireless light communication system using a modulating retro-reflector (MRR) enables asymmetric optical links, which forms a two-way optical link using a single transmitter and receiver. Here, in association with an MRR, we propose, fabricate, and characterize asymmetric optical links using monolithic III-nitride diodes, where one III-nitride diode functions as a transmitter to emit light, an MRR reflects light with the encoded information, another monolithically integrated III-nitride diode serves as a receiver to absorb the reflected light to convert optical signals into electrical ones, and the encoded information is finally decoded. Advanced monolithic III-nitride asymmetric optical links can be developed toward Internet of Things (IoT) deployment based on such multifunction devices.
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.
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