Abstract
A new polarimeter is presented which gives time-resolved measurements of both the optic-axis angle and the linear phase retardation for modulated birefringent optical devices. It is suitable for characterizing dynamic waveplate devices based on liquid crystal and other materials. It is fully automated and requires no angular alignment of the device under test. The system has an absolute angle error of < ± 0.3° and a retardance error of < ± 0.44°, with considerably better relative accuracy. The method has been tested with a chiral nematic liquid crystal device exhibiting flexoelectro-optic switching at 3 kHz in the uniform lying helix mode. These results represent the first time-resolved tilt-angle and phase retardation measurements for a liquid crystal device operating at fast switching frequencies.
Highlights
Optical devices which allow their birefringent properties to be dynamically controlled have many technological applications
Liquid crystal (LC) devices are attractive for birefringent switching as they can be fabricated in planar arrays of pixels which are driven from an electrical backplane and used in a reflective configuration
Chiral nematic LC devices utilizing the flexoelectro-optic effect [5], are of particular interest for SLMs [1,4], as they are birefringent devices in which the angle of the optic-axis may be modulated with comparatively fast switching frequencies >1 kHz
Summary
Optical devices which allow their birefringent properties to be dynamically controlled have many technological applications. A feature of many LC devices is that they need to be driven with a bipolar electric field to prevent ionic screening effects As they cannot be held in a static state, this precludes the use of polarimeters which rely on the polarization state remaining constant for the duration of the measurement. Employing the rotating analyzer method to measure the tilt-angle of the optic-axis during flexoelectro-optic switching in a chiral nematic LC is likely to introduce considerable measurement error due to ionic screening effects. We present a new method for measuring the time-resolved angle of the optic-axis and the linear retardance under dynamic switching conditions, which overcomes the aforementioned limitations.
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