High‐Purity Circularly Polarized Lasing From Chiral VCSELs With Aligned Semiconductor Quantum Wells

Abstract Circularly polarized light (CPL) is vital for optical communication, quantum information, 3D displays, and bioimaging. Traditional CPL generation using linear polarizers and quarter‐wave plates suffers from significant energy loss. Here, we present a chiral vertical‐cavity surface‐emitting laser (VCSEL) by integrating face‐down aligned CdSe/CdZnS colloidal quantum wells (CQWs, also known as nanoplatelets) with a cholesteric liquid crystal (CLC)‐based distributed Bragg reflectors (DBRs). The CLC reflectors selectively reflect CPL matching their handedness, enhancing lasing, and ensuring a dominant output of the same handedness. The face‐down aligned CQWs offer i) directional emission for precise spectral matching with the CLC‐DBR stop band and ii) optimized light‐matter coupling via dipole alignment with cavity modes. This leads to a lower lasing threshold and high polarization dissymmetry, achieving a |g‐factor| of 1.9. The lasing process further amplifies circular polarization asymmetry, increasing the right‐CP ( R ‐CP) to left‐CP ( L ‐CP) intensity ratio from 0.21 in fluorescence to 41.7 in lasing. Furthermore, we demonstrate flexible chiral VCSELs with mechanically tunable emission wavelengths while maintaining performance. Our approach provides an efficient and customizable strategy for next‐generation high‐purity CPL sources, paving the way for advanced photonic applications.