Recently we demonstrated a novel and simplified model enabling to calculate the voltage dependent retardance provided
by parallel aligned liquid crystal devices (PA-LCoS) for a very wide range of incidence angles and any wavelength in the
visible. To our knowledge it represents the most simplified approach still showing predictive capability. Deeper insight
into the physics behind the simplified model is necessary to understand if the parameters in the model are physically
meaningful. Since the PA-LCoS is a black-box where we do not have information about the physical parameters of the
device, we cannot perform this kind of analysis using the experimental retardance measurements. In this work we
develop realistic simulations for the non-linear tilt of the liquid crystal director across the thickness of the liquid crystal
layer in the PA devices. We consider these profiles to have a sine-like shape, which is a good approximation for typical
ranges of applied voltage in commercial PA-LCoS microdisplays. For these simulations we develop a rigorous method
based on the split-field finite difference time domain (SF-FDTD) technique which provides realistic retardance values.
These values are used as the experimental measurements to which the simplified model is fitted. From this analysis we
learn that the simplified model is very robust, providing unambiguous solutions when fitting its parameters. We also
learn that two of the parameters in the model are physically meaningful, proving a useful reverse-engineering approach,
with predictive capability, to probe into internal characteristics of the PA-LCoS device.
|