Fig. 1. Fabrication and structural diagram of AlGaInP-based photodetector sensor. (a) SEM image of diode device, with red square indicating magnified view of active region; (b) diagram of optical path comparison between concentric ring structure and square structure; (c) optical image of fabricated photodetector sensor, with red and yellow squares highlighting magnified details of electrode wiring positions

Fig. 2. Process flow of AlGaInP-based optoelectronic pulse wave sensor (insets show optical images of chip under 10 mA drive current, depicting two different modes: inner circle emission/outer ring detection and outer ring emission/inner circle detection)

Fig. 3. Optoelectronic characteristics of pulse wave sensor. (a) I-V curves of outer ring detector when inner circle diode is used as emitter operating at different currents from 0 to 50 mA; (b) I-V curves of inner-circle detector when outer-circle diode is used as emitter, operating at different currents from 0 to 50 mA; (c) photocurrent of detector extracted from Figs. 3(a) and 3(b) varying with emitter current; (d) I-V characteristic curves and EQE of LED

Fig. 4. Electroluminescence (EL) spectra of LED and spectral responsivity of photodetector. (a) EL spectra of LED operating at drive currents ranging from 10 mA to 80 mA; (b) peak wavelengths and FWHMs of spectra at drive currents ranging from 10 mA to 80 mA; (c) EL spectra of LED and unbiased normalized spectral responsivity of PD at bias currents from 10 mA to 50 mA

Fig. 5. Working mechanism of pulse detection sensor and experimental setup. (a) Working mechanism of pulse detection sensor; (b) diagram of pulse detection sensor and experimental setup

Fig. 6. Performance of pulse wave signal detection sensor. (a) Quantization relation of signal amplitude when driving current of LED is from 20 mA to 50 mA; (b) amplified information of heart pulse waveform when driving current is 50 mA; (c) photocurrent varitation of sensor working continuously for 16.5 h