Structural symmetry breaking induced polarization sensitivity enhancement: Used for THz tri-band mechanical tunability

Abstract

A symmetry broken hexagram metamaterial (SBHM) is presented to enhance the polarization sensitivity, and thus realize mechanically controlling the transmissions of tri-band in terahertz (THz) region. This SBHM has different electromagnetic response for rotating clockwise and anticlockwise, respectively. When incident THz wave is polarized in the direction of [Formula: see text], the SBHM has three stopbands with central frequencies at 0.36 THz, 0.52 THz and 0.75 THz, respectively. When the SBHM rotates clockwise [Formula: see text], the transmission of 0.52 THz increases from 0.17 to 0.85, and its modulation depth reaches 68%. On the contrary, when it rotates anticlockwise [Formula: see text], the transmissions of the other two bands can be modulated simultaneously, and their modulation depth are 78% and 40%, respectively. The physical mechanism for the tunability is investigated using finite-integration time-domain (FITD) method. The results indicated that the tri-band tunability in the SBHM is due to the mode transfer and polarization sensitivity enhancement which is induced by near field coupling. This novel design proves a new way for modulation, selection and switching of the THz wave at multiband.