Polarized terahertz electromagnetic-wave radiation from cuprate superconductor Bi2212 mesa structures

Polarized terahertz (THz) sources are important components in THz technologies. This paper highlights and discusses recent progress and measurement methods in the monolithic generation of polarized THz radiation using intrinsic Josephson junction oscillators made of high-T _c superconductors. The polarized radiation is generated from three mesa designs: truncated-edge square, notched cylindrical, and rectangular mesa structures. The polarization control depends on the excitation of two orthogonal TM modes in these mesas, comprising stacked intrinsic Josephson junctions in single crystalline Bi₂Sr₂CaCu₂O_8+δ . This method maintains a high output intensity and low axial ratios while avoiding the signal loss associated with external polarimetric modulators prevalent in the THz frequency range. Moreover, it demonstrates the manipulation of terahertz wave helicity by adjusting the current injection position, with experiments substantiating the device’s capability to switch between left-handed and right-handed elliptical polarization at designated frequencies.