Split-ring resonator metamaterial with electrostatically tunable gaps for enhanced InGaAsP photodetector performance at telecommunication wavelengths

This work presents an InGaAsP/InP photodetector enhanced by an electrically tunable split-ring resonator (SRR) metamaterial, enabling voltage-controlled spectral response in the telecommunication band. The SRR array, fabricated in a 50 nm gold layer with tunable nanogaps, modulates its resonance through electrostatic actuation in the range of −10 V to +10 V, achieving precise control over responsivity and quality factor without altering the device footprint. Three-dimensional finite-difference time-domain simulations confirm strong field confinement within the SRR gaps and efficient coupling to the underlying absorber, consistent with experimental responsivity spectra. Measured baseline responsivity at 1.55 µm is 0.71 A/W, obtained under zero-bias conditions in the fabricated device. This value agrees with the simulated baseline response, while particle-swarm-optimized simulations predict a maximum responsivity of 1.25 A/W at the optimal tuning voltage, reflecting the combined effect of sub-wavelength field confinement and SRR–absorber coupling. The extracted quality factor increases from 28.5 to 35.2 with applied bias, while wavelength-shift sensitivity reaches ∼0.43 nm/V. These results demonstrate that integrating an electrostatically tunable metamaterial layer with a high-speed photodetector can provide dynamic spectral selectivity and controlled performance tuning, offering potential for adaptable optical communication and sensing systems.