Circularly Polarized Stimulated Emission from a Chiral Cavity Based on Apparent Circular Dichroism Organic Thin Films

The lack of intrinsic mirror symmetry in cavity mirrors poses a significant challenge for most organic chiral materials in generating circularly polarized (CP) lasers. However, nonreciprocal chiroptical materials, such as recently developed organic thin films exhibiting apparent circular dichroism (ACD), provide a promising approach to CP light generation. In this work, we integrate an ACD-based thin film into a free-space dye laser cavity, achieving direct CP laser emission with a degree of circular polarization (DOCP) up to 0.6, corresponding to a dissymmetry factor (glum) of 1.2, a new record for organic chiral lasers. The degree of polarization (DOP) is close to 0.8, and the observed ellipticity in the emitted light originates from the ACD effect in the thin film, leading to asymmetric cavity losses for right- and left-circularly polarized light. This breakthrough demonstrates the potential of ACD-based materials to overcome the limitations of conventional chiral laser systems, marking a significant advancement in the field and paving the way for next-generation chiral photonic devices.