Wide-field Spectroscopic Imaging of Optical Activity

Optical activity spectroscopy techniques, such as circular dichroism (CD) and optical rotatory dispersion (ORD), are essential for probing the chiral properties of molecules and materials. However, conventional implementations of these methods, while highly sensitive, typically require large sample volumes and provide only ensemble-averaged information, limiting their ability to resolve spatial heterogeneity. Imaging-based approaches can overcome this limitation but often rely on time-consuming point scanning and complex instrumentation. To address these challenges, this thesis explores digital holography as a versatile platform for wide-field chiral imaging. By capturing both amplitude and phase information of the optical field, holography enables quantitative characterization of chiroptical effects and supports polarization multiplexing to achieve robust measurements across extended fields of view. Two complementary holographic systems were developed: an off-axis configuration for quantitative wide-field measurements and an inline configuration designed for high sensitivity and simplicity. Both platforms employ polarization-sensitive detection schemes based on spatial lock-in to minimize artifacts and enhance stability. The off-axis system retrieves the full complex optical field from a single acquisition, enabling simultaneous imaging of CD and ORD across large fields of view and allowing quantitative mapping of chiral contrast, including resolving enantiomeric excess in structured samples. The inline system reduces speckle noise and achieves single-particle sensitivity by operating with partially coherent light, enabling parallel detection of chiral signals from multiple nanoparticles and uncovering their spectral heterogeneity. These results establish digital holography as a powerful approach for bridging the gap between ensemble spectroscopy and high-resolution wide-field chiral imaging, opening new avenues for the study of complex biological and material systems.