Switchable Spin-Selective Transmission in Nano-Kirigami Metasurfaces

Polarization control and modulation of optical signals play a crucial role in optical information transmission, with widespread applications in optical communication, sensing, and signal processing. Here, we propose an intrinsically chiral nano-kirigami metasurface featuring out-of-plane twisting, which enables switchable spin-selective light transmission. At the operating wavelength, it nearly completely blocks the transmission of one type of circularly polarized light while maintaining a transmission exceeding 70% for the other type. Crucially, by merely adjusting the rotation angles or deformation heights of the four arms of the nano-kirigami structures, the metasurface can switch from selective transmission of left-handed circularly polarized light to right-handed circularly polarized light, and vice versa, without the need for dramatic structural geometric chirality changes through mirror operations. Simultaneously, a remarkable circular dichroism of up to 0.74 is achieved, and its sign reverses with the transition of transmission. Electromagnetic multipolar analysis reveals that this switching of chiral response is governed by handedness-dependent excitations of toroidal dipole modes. Additionally, the spin-encoded near-field imaging results demonstrate the potential applications of this switchable spin-selective transmission based on nano-kirigami metasurfaces in digital imaging and chiroptical encryption.