Combining Soft with Hard Condensed Matter for Circular Polarized Light Sensing and Logic Operations

The study shows the incorporation of chiral nematic photonic cellulose nanocrystal (CNC) films, well known for their adaptive character of selective reflection of circular polarized light (CPL), and silicon-based thin-film photodiodes, thus achieving a light sensor capable of discriminating right- from left-handed CPL. The circular polarization (CP) response is maximum for specific wavelengths in the green-to-red region. When subjected to these wavelengths, they produce photocurrents that are over 50% distinct between the two CP states. Proper signal processing, thus, yields a binary output depending on the handedness of the light. Through the addition of monovalent salt to the initial CNC suspension, a blueshift to the photonic band gap is induced, enabling a larger wavelength gamut and application possibilities. The measured results are then used as a basis for electromagnetic simulations that show remarkable consistency with the experimental results, thus defining a new tool that can be used to efficiently optimize the devices’ response. Fast transient responses to CPL are shown with possible logic operations, as well as humidity sensing. The developed devices are, thus, applicable in areas as diverse as imaging, CPL sensing, optoelectronic counterfeiting, and information processing with logic states that depend solely on the handedness of the incident light.