Electrically Reconfigurable Optical Initialization of Spin Valley Polarization in Monolayer WS 2 Enabled by Switchable Dual‐Mode Liquid Crystal Lasers

ABSTRACT An electrically reconfigurable platform for optical initialization and active switching of spin valley polarization in two dimensional (2D) materials, such as monolayer , is proposed and demonstrated, which was made possible by the integration of 2D semiconductor with self‐assembled dual‐mode laser based on dye‐doped chiral liquid crystals (DDCLCs). By applying voltage‐driven phase transitions between the blue phase II (BPII) with a simple cubic structure and the focal‐conic state of the chiral nematic (N*) phase, the emission helicity of the DDCLC laser can be reversibly switched between circularly polarized band‐edge lasing and unpolarized random lasing. In the BPII state, the system emits left‐handed circularly polarized lasing that selectively excites valley‐polarized excitons in , yielding a steady‐state degree of circular polarization (DoCP) of 20.13% and a peak transient DoCP of 27%, as measured by time‐resolved photoluminescence (TRPL). Transitioning to the N* phase by electrical tuning removes the helicity from the excitation, thereby suppressing valley polarization. This lasing mode switching is fully reversible and occurs within sub‐millisecond timescales. Our findings establish a novel approach to reconfigurable, optically mediated valleytronic control through photonic band‐structure engineering, offering broad potential for polarization‐sensitive optoelectronic and quantum technologies.