Optically Modulated Multiband Terahertz Perfect Absorber

Development of tunable, dynamic, and broad bandwidth metamaterialdesigns is a keystone objective for metamaterials research, necessary for thefuture viability of metamaterial optics and devices across the electromagneticspectrum. Yet, overcoming the inherently localized, narrow bandwidth, andstatic response of resonant metamaterials continues to be a challengingendeavor.

Resonant perfect absorbers have flourished as one of the mostpromising metamaterial devices with applications ranging from power har-vesting to terahertz imaging. Here, an optically modulated resonant perfectabsorber is presented. Utilizing photo-excited free carriers in silicon padsplaced in the capacitive gaps of split ring resonators, a dynamically modu-lated perfect absorber is designed and fabricated to operate in reflection.Large modulation depth (38% and 91%) in two absorption bands (with 97%and 92% peak absorption) is demonstrated, which correspond to the LC(0.7 THz) and dipole (1.1 THz) modes of the split ring resonators.