Enhanced Circularly Polarized Lasing in Nanocellulose-Silica Composites

Abstract

Crystalline nanocellulose (CNC) is a nanometric form of cellulose known for its cholesteric structure, imparting circular dichroism to the material. CNC has been used in many photonic applications, exploiting its chiroptical properties to produce circularly polarized photoluminescence. In this work, an insightful characterization of the polarimetric response of nanocrystalline cellulose created through the scalable process of vacuum filtration is performed. This study confirms the strong dichroic character of the nanocellulose films but also reveals a significant linear dichroism contribution, which in turn limits the use of the material to produce a higher degree of circularly polarized light. Here, it is demonstrated that the incorporation of silica nanospheres into the CNC matrix significantly reduces the linear dichroism in the film. More importantly, the decrease in linear diattenuation correlates with an increase in circular dichroism, leading to samples with improved performance as circular polarizers (circular diattenuator). The enhanced chiroptical response of the silica-nanocellulose composites is demonstrated by building a chiral lasing system consisting of a thin layer of resist containing an organic dye (rhodamine B) enclosed between two layers of nanocrystalline cellulose. A maximum photoluminescence dissymmetry factor of 0.57 is observed at the wavelength of 611 nm.