Showing papers by "Jeroen Beeckman published in 2017"
TL;DR: In this article, the long-range correlation that characterizes nematic liquid crystals is taken into account in the thermal noise, and it is possible to account for the spatial oscillations and propagation losses experienced by nematicons.
Abstract: Starting from the de Gennes theory of director fluctuations in nematics, we report on a model of the spatial fluctuations in nematicon propagation. We demonstrate that, when the long-range correlation that characterizes nematic liquid crystals is taken into account in the thermal noise, it is possible to account for the spatial oscillations and propagation losses experienced by nematicons. Increasing the power of the nematicon, the oscillation amplitudes increase and the propagation losses decrease. The nematicon is then more strongly confined and deviates more, but is less scattered by the thermally induced perturbations of the refractive index. All the results are in good agreement with the experimental observations.
13 citations
TL;DR: In this paper, the authors developed a model to simulate the RC-effects with an approximate model, where the resistivity of the conductive layers and the dielectric properties of the liquid crystal are coupled.
Abstract: Liquid crystals are mostly known for their use in displays, but over the past decade these materials have been applied in a number of other devices such as tunable lenses or beam steering devices. A common technique to realize a gradual electric field profile as is required to obtain a gradual refractive index profile in these applications is the use of weakly conductive materials. The weakly conductive layers are able to spread the voltage profile which is applied through well-conductive electrodes at the side of the weakly conductive layer. The simulation and design of such structures is not trivial because two or three dimensional quasi-static electric field profiles need to be calculated. This is due to the fact that the resistivity of the conductive layers and the dielectric properties of the liquid crystal are coupled. An exact solution requires solving a number of coupled differential equations. In this paper, we develop a model to simulate the RC-effects with an approximate model.
13 citations
14 May 2017
TL;DR: In this article, a low-loss PZT-on-SiN waveguide platform was used for low-frequency modulation using a ring resonator, achieving a bandwidth surpassing 25 GHz.
Abstract: Electro-optic modulation using a low-loss PZT-on-SiN waveguide platform is demonstrated. Using a ring resonator a V π L π of 1 Vcm is demonstrated. Small-signal measurements have demonstrated a bandwidth surpassing 25 GHz.
12 citations
TL;DR: In this article, a hybrid luminescent layer is produced based on a mixture of CdSe/CdS nanorods dispersed in a liquid crystal that is aligned by an electric field and polymerized by UV illumination.
Abstract: Semiconductor nanorods have anisotropic absorption and emission properties. In this work a hybrid luminescent layer is produced based on a mixture of CdSe/CdS nanorods dispersed in a liquid crystal that is aligned by an electric field and polymerized by UV illumination. The film emits light with polarization ratio 0.6 (polarization contrast 4:1). Clusters of nanorods in liquid crystal can be avoided by applying an AC electric field with sufficient amplitude. This method can be made compatible with large-scale processing on flexible transparent substrates. Thin polarized light emitters can be used in LCD backlights or solar concentrators to increase the efficiency.
9 citations
TL;DR: In this paper, a polarization independent and fast electrically switchable beam steering device is presented, based on a surface relief grating combined with polymer-stabilized blue phase liquid crystals.
Abstract: A polarization independent and fast electrically switchable beam steering device is presented, based on a surface relief grating combined with polymer stabilized blue phase liquid crystals. Switching on and off times are both less than 2 milliseconds. The prospects of further improvements are discussed. Full Text: PDF References D.C. Wright, et al., "Crystalline liquids: the blue phases", Rev. Mod. Phys. 61, 385 (1989). CrossRef H. Kikuchi, et al., "Polymer-stabilized liquid crystal blue phases", Nat. Mater. 1, 64 (2002). CrossRef Samsung, Korea, SID exhibition, (2008). J. Yan, et al., "Direct measurement of electric-field-induced birefringence in a polymer-stabilized blue-phase liquid crystal composite", Opt. Express 18, 11450 (2010). CrossRef L. Rao, et al., "A large Kerr constant polymer-stabilized blue phase liquid crystal", Appl. Phys. Lett. 98, 081109 (2011). CrossRef Y. Hisakado, et al., "Large Electro-optic Kerr Effect in Polymer-Stabilized Liquid-Crystalline Blue Phases", Adv. Mater. 17, 96 (2005). CrossRef K. M. et al., "Submillisecond Gray-Level Response Time of a Polymer-Stabilized Blue-Phase Liquid Crystal", J. Disp. Technol. 6, 49 (2010). CrossRef Y. Chen, et al., "Level set based topology optimization for optical cloaks", Appl. Phys. Lett. 102, 251106 (2013). CrossRef H. Choi, et al., "Fast electro-optic switching in liquid crystal blue phase II", Appl. Phys. Lett. 98, 131905 (2011). CrossRef Y.H. Chen, et al., "Polarization independent Fabry-Perot filter based on polymer-stabilized blue phase liquid crystals with fast response time", Opt. Express 19, 25441 (2011). CrossRef Y. Li, et al., "Polarization independent adaptive microlens with a blue-phase liquid crystal", Opt. Express 19, 8045 (2011). CrossRef C.T. Lee, et al., "Design of polarization-insensitive multi-electrode GRIN lens with a blue-phase liquid crystal", Opt. Express 19, 17402 (2011). CrossRef Y.T. Lin, et al., "Mid-infrared absorptance of silicon hyperdoped with chalcogen via fs-laser irradiation", J. Appl. Phys. 113, (2013). CrossRef J.D. Lin, et al., "Spatially tunable photonic bandgap of wide spectral range and lasing emission based on a blue phase wedge cell", Optics Express 22, 29479 (2014). CrossRef W. Cao, et al., "Lasing in a three-dimensional photonic crystal of the liquid crystal blue phase II", Nat. Mat. 1, 111 (2002). CrossRef S.T. Hur, et al., "Liquid-Crystalline Blue Phase Laser with Widely Tunable Wavelength", Adv. Mater. 25, 3002 (2013). CrossRef A. Mazzulla, et al., "Thermal and electrical laser tuning in liquid crystal blue phase I", Soft. Mater. 8, 4882 (2012). CrossRef C.W. Chen, et al., "Random lasing in blue phase liquid crystals", Opt. Express 20, 23978 (2012). CrossRef O. Willekens, et al., "Ferroelectric thin films with liquid crystal for gradient index applications", Opt. Exp. 24, 8088 (2016). CrossRef O. Willekens, et al., "Reflective liquid crystal hybrid beam-steerer", Opt. Exp. 24, 1541 (2016). CrossRef M. Jazbinsek, et al., "Characterization of holographic polymer dispersed liquid crystal transmission gratings", J. Appl. Phys. 90, 3831 (2001). CrossRef C.C. Bowley, et al., "Variable-wavelength switchable Bragg gratings formed in polymer-dispersed liquid crystals", Appl. Phys. Lett. 79, 9 (2001). CrossRef Y.Q. Lu, et al., "Polarization switch using thick holographic polymer-dispersed liquid crystal grating", Appl. Phys. 95, 810 (2004). CrossRef J.J. Butler et al., "Diffraction properties of highly birefringent liquid-crystal composite gratings", Opt. Lett. 25, 420 (2000). CrossRef R.L. Sutherland et al., "Electrically switchable volume gratings in polymer-dispersed liquid crystals", Appl. Phys. Lett. 64, 1074 (1994). CrossRef X. Shang, et al., "Electrically Controllable Liquid Crystal Component for Efficient Light Steering", IEEE Photo. J. 7, 1 (2015). CrossRef J. Yan, et al., "Extended Kerr effect of polymer-stabilized blue-phase liquid crystals", Appl. Phys. Lett. 96, 071105 (2010). CrossRef H.S. Chen, et al., "Hysteresis-free polymer-stabilized blue phase liquid crystals using thermal recycles", Opt. Mat. Exp. 2, 1149 (2012). CrossRef J. Yan. et al., "Dual-period tunable phase grating using polymer stabilized blue phase liquid crystal", Opt. Lett. 40, 4520 (2015). CrossRef H.S. Chen, et al., "Hysteresis-free polymer-stabilized blue phase liquid crystals using thermal recycles", Opt. Mat. Exp. 2, 1149 (2012). CrossRef H.C. Cheng, et al., "Blue-Phase Liquid Crystal Displays With Vertical Field Switching", J. Disp. Technol. 8, 98 (2012). CrossRef
5 citations
IMEC1
TL;DR: In this article, the authors report on new materials that can be monolithically integrated on high-index contrast silicon or silicon nitride photonic ICs to enhance their functionality, including graphene and other 2D-materials for realizing compact electroabsorption modulators and non-linear devices, ferroelectric materials for realizing phase modulators, and adiabatic couplers for realizing bistable switches.
Abstract: In this presentation we will report on our recent work on new materials that can be monolithically integrated on high-index contrast silicon or silicon nitride photonic ICs to enhance their functionality. This includes graphene and other 2D-materials for realizing compact electro-absorption modulators and non-linear devices, ferroelectric materials for realizing phase modulators and adiabatic couplers for realizing bistable switches.
2 citations
TL;DR: In this article, the spatial instabilities in nematicon propagation are modeled with a correlated noise and the long range interaction in liquid crystals is taken into account with the correlated noise.
Abstract: We present modeling of the spatial instabilities in nematicon propagation where the long range interaction in liquid crystals is taken into account with a correlated noise. The experimental measurements support the numerical results.