Fast-response and scattering-free polymer network liquid crystals for infrared light modulators

Abstract

A fast-response and scattering-free homogeneously aligned polymer network liquid crystal (PNLC) light modulator is demonstrated at λ=1.55 μm wavelength. Light scattering in the near-infrared region is suppressed by optimizing the polymer concentration such that the network domain sizes are smaller than the wavelength. The strong polymer network anchoring assists LC to relax back quickly as the electric field is removed. As a result, the PNLC response time is ∼250× faster than that of the E44 LC mixture except that the threshold voltage is increased by ∼25×.

Variable optical attenuator with a polymer-stabilized dual-frequency liquid crystal

“…At f ϭ 1 kHz, the optical threshold voltage of the PSDFLC ͑V th ϳ 8.5 V rms ͒ is much higher than that of the pure DFLC because of the polymer network effect. 5 As the applied voltage increases, light scattering gradually increases so that the transmittance decreases. The photodetector was set at 7 cm behind the second beam displacer, which corresponds to 1.2°acceptance angle.…”

“…6 -10 On the other hand, the scattering-free PSLC is particularly attractive for phase modulation in the near-infrared region. 5 In spite of the need for amplitude or phase modulation, a fast response time is a standard requirement. This is particularly problematic for VOAs operating in the near-infrared region ͑ ϭ 1.55 m͒, where a larger cell gap is required, which results in a longer response time.…”

“…Both anisotropic scattering 4 and scattering-free 5 PSLC systems have been developed, depending on the polymer concentration and operating wavelength. The anisotropic light-scattering PSLC is useful for amplitude modulation because it has, e.g., a reflective display, switchable polarizer, and variable optical attenuator (VOA).…”

Memory effect of polymer dispersed liquid crystal by hybridization with nanoclay

“…Improved electro-optical properties have been reported for new applications [3,4]. Fan et al [5] reported scattering-free PDLC for infrared light modulator. Nicoletta et al [6] investigated application of PDLC for electro-chromic device by doping some electro-chromic materials.…”

Cell Gap Effect on the Dynamics of Liquid Crystal Phase Modulators

“…To achieve a fast response time, low rotational viscosity (c 1 ) LC mixtures are preferred [9][10][11]. Another straightforward approach is to use a thin cell gap filled with a high birefringence (Dn) and low viscosity LC mixture [12][13]. The LC directors rise time s rise and decay time s decay are known to be proportional to d 2 , where d is the cell gap.…”