A photoexcited tunable circular dichroism with planar chiral metamaterial in terahertz region

We proposed a tunable planar chiral metamaterial (PCMM) which can achieve a giant and photoexcited tunable circular dichroism (CD) effect. The tunable PCMM is composed of an array of conjugated bilayer wheel structures integrated photoconductive silicon (Si). The conductivity of photoconductive Si pads filled in the gap of wheel structures can be tuned efficiently through illumination with different pump power of infrared light. This results in the modulation of CD effect with modulation depths of 80.6% and 64.3% at 0.93 THz and 1.49 THz, respectively. Due to the tunable CD effect, the proposed PCMM could find many potential applications in integrated terahertz spectroscopic, sensing and imaging devices.