A scattered light polarimetry (LSP) sub-system of a hybrid system for characterizing stress in a chemically-strengthened (CS) substrate having a top-surface and a near-surface waveguide, includes a LSP light source system, an LSP light source actuator coupled to the LSP light source system, and an optical compensator within an optical path of a LSP laser beam emitted by the LSP light source system. The optical compensator includes a half-wave plate, a half-wave plate actuator, a diffuser, and a diffuser actuator. The LSP sub-system further includes a LSP detector system in optical communication with the optical compensator through an LSP coupling prism having a LSP coupling surface, a focusing lens and a focusing lens actuator, and a support plenum having a surface and a measurement aperture, the support plenum configured to support the CS substrate at a measurement plane at the measurement aperture, and to operably support the LSP coupling prism.