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- Engström, David, 1976, et al.
(author)
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Analog low-loss full-range phase modulation by utilizing a V-shaped switched ferroelectric liquid-crystal cell in reflective mode
- 2006
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In: Optics Letters. - 0146-9592 .- 1539-4794. ; 31:19, s. 2906-2908
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Journal article (peer-reviewed)abstract
- We have studied the analog (V-shaped switching) mode in ferroelectric liquid crystals in reflective mode for analog phase modulation applications. We have found that several combinations of cell thicknesses and input polarization states exist for which near-lossless analog phase modulation with a range of ~2π rad is obtained, and we demonstrate one such combination experimentally. Despite a slight deviation from the ideal conditions, e.g., the tilt angle was 38° instead of the desired 45°, virtually pure 1.6π rad phase modulation was obtained; the measured values agree very well with our numerical simulations of the real device.
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- Engström, David, 1976, et al.
(author)
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Three-level phase modulator based on orthoconic antiferroelectric liquid crystals
- 2006
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In: Optics Letters. - 0146-9592 .- 1539-4794. ; 31:21, s. 3158-3160
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Journal article (peer-reviewed)abstract
- Surface-stabilized orthoconic antiferroelectric liquid crystals (OAFLCs) have a director tilt of θ=45° and are, with no field applied, negatively uniaxial with the optic axis perpendicular to the cell substrates. We demonstrate that OAFLCs can be utilized to achieve lossless phase modulation with three almost equidistant phase levels. This turns out to be true also for polymer-stabilized OAFLCs, where the polymer network increases the switching speed of the device without affecting the phase modulation appreciably.
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- Engström, David, 1976, et al.
(author)
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Diffraction-based determination of the phase modulation for general spatial light modulators
- 2006
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In: Applied Optics. - 1539-4522. ; 45:28, s. 7195-7204
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Journal article (peer-reviewed)abstract
- We describe a characterization method based on diffraction for obtaining the phase response of spatial light modulators (SLMs), which in general exhibit both amplitude and phase modulation. Compared with the conventional interferometer-based approach, the method is characterized by a simple setup that enables in situ measurements, allows for substantial mechanical vibration, and permits the use of a light source with a fairly low temporal coherence. The phase determination is possible even for a SLM with a full amplitude modulation depth, i.e., even if there are nulls in the amplitude transmission characteristic of the SLM. The method successfully determines phase modulation values in the full 2pi rad range with high accuracy. The experimental work includes comparisons with interferometer measurements as well as a SLM characterization with a light-emitting diode (LED).
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