Abstract Wearable photoplethysmography (PPG) demands stable, long-term light emitters capable of operating under continuous skin contact. Vertical-cavity surface-emitting lasers (VCSELs) offer narrow spectral linewidths, directional emission, and low power consumption; however, conventional devices incorporating thick distributed Bragg reflector (DBR) stacks exhibit mechanical rigidity and inefficient heat dissipation. Here, we present a 6.6-µm-thick ultrathin VCSEL operating at 930 nm, integrated with a near-infrared organic photodetector (NIR-OPD) on a skin-conformal elastomer substrate. A copper-plated heatsink enabled efficient heat dissipation and optical feedback, achieving lasing with only 18 n-DBR. The device emitted 8.25 mW peak power with a 4.53 nm linewidth, retaining 99.3% output over 12 h with minimal heating (1.3 °C). It preserved 97.8% output after 500 bending cycles (6 mm radius) and caused negligible skin irritation. Co-integration with near-infrared OPD enabled stable PPG signal acquisition with <5% amplitude variation, establishing a robust VCSEL–OPD PPG sensor for next-generation wearable biosignal monitoring.
Yook et al. (Sat,) studied this question.