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High order magnetic and electric resonant modes of split ring resonator metasurface array 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 due to the high potential for different application. In this work, we study photodetection enhancement of these resonant modes of U-shape SRR array 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 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 tuneable enhancement of photoresponse are also demonstrated. The remarkable enhancement makes mid-infrared photodetection possible to operate at room temperature.