Optically tunable metamaterial perfect absorber on highly flexible substrate

•A flexible, optically tunable, THz metamaterial perfect absorber is reported.•The device was fabricated using semiconductor transfer technique with high yield.•The absorber was characterized by terahertz time domain spectroscopy.•The absorptivity of the device may be efficiently tuned using an optical pump beam.

We present our recent progress on a highly flexible tunable perfect absorber at terahertz frequencies. Metamaterial unit cells were patterned on thin GaAs patches, which were fashioned in an array on a 10 μm thick polyimide substrate via semiconductor transfer technique, and the backside of the substrate was coated with gold film as a ground plane. Optical-pump THz-probe reflection measurements show that the absorptivity can be tuned up to 25% at 0.78 THz and 40% at 1.75 THz through photo-excitation of free carriers in GaAs layers in presence of 800 nm pump beam. Our flexible tunable metamaterial perfect absorber has potential applications in energy harvesting, THz modulation and even camouflages coating.