High Order Magnetic and Electric Resonant Modes of Split Ring Resonator Metasurface Arrays for Strong Enhancement of Mid-Infrared Photodetection

Integration of photonic nanostructures with optoelectrical semiconductors offers great potential of developing high sensitivity and multifunctional photodetectors enabled by enhanced light–matter interactions. Split ring resonator (SRR) array which resonates at different resonant modes, including fundamental magnetic mode (m₀), high order magnetic mode (m₁), and electric (e) mode has been investigated because of the high potential for different applications. In this work, we study photodetection enhancement of these resonant modes of U-shape SRR arrays in the mid-infrared (2–5 μm) range and report, for the first time, the strong enhancement of photodetection by superimposition of m₁ and e modes in an integrated photodetector consisting of a U-shape SRR array and an InAsSb-based heterojunction photodiode. We observe that the m₁ mode in the SRR array shows the strongest enhancement of photocurrent, sequentially followed by the e and m₀ modes. Using superimposed m₁ and e modes, about an order of enhancement in room temperature detectivity (to about 2.0 × 10¹⁰ Jones) is achieved under zero-power-supply without sacrificing the response speed. In addition, polarization-resolved photoresponse between m₁ and e modes and tunable enhancement of photoresponse are also demonstrated. The remarkable enhancement makes mid-infrared photodetection possible to operate at room temperature.