Fast Light Modulators Research Articles

Volumetric random-access multi-focus scanning based on fast light modulation

Highly efficient scanning of focused light in the three-dimensional space is of great significance in many fields, such as volumetric biomedical imaging, laser beam machining, and optical metrology. Here we propose light-modulation-based volumetric multi-focus scanning (LM-VMS) by generating a complex field superposed of multiple spherical wave components. Each spherical wave component corresponds to a focus, and can be modulated independently by changing its tilt term and defocus term. Therefore, the positions of all the foci can be manipulated in a random-access scan mode. We showed the excellent performance of LM-VMS in a scanning system based on a digital micromirror device. This system had a lateral scanning radius of 2.43 mm and a longitudinal scanning range of 140 mm. Its lateral resolution in the focal plane was 28.1 ± 0.4 μm. Furthermore, we demonstrated that LM-VMS could scan 24 foci simultaneously along independent, arbitrary trajectories at a rate of 22.7 kHz. LM-VMS is a promising solution for optical random-access scan to considerably accelerate the information acquisition and machining in various industrial applications.

Theoretical investigation of the photochromic properties of [2.2]paracyclophane-bridged imidazole dimers and bis(imidazole) dimers

[2.2]paracyclophane-bridged imidazole dimers are excellent candidates to build fast photochromic devices with practical applications in full–colour holographic display. Herein, we propose an accurate, yet affordable, computational protocol relying on (TD-)DFT for investigating the structural, thermodynamical and optical properties of these systems, three properties of fundamental importance for their potential applications in fast light modulator devices. Within this theoretical framework, we provide an interpretation of the stepwise two-photon photochromic reaction observed for a symmetric [2.2]paracyclophane-bridged bis(imidazole dimer) and propose a new dissymmetric dimer with potential wavelength-dependent photoactivity.

Compensation for the spectral dispersion of light polarization states in electro-optic modulators based on chiral liquid crystals

The effect of compensation for the spectral dispersion of light polarization states at the output of a single-domain layer of a chiral liquid crystal (CLC) is experimentally studied. It is shown that such dispersion can be decreased significantly with the aid of phase plates of two types that have different signs of the spectral dispersion of birefringence. The dispersion compensation allows one to significantly increase the operating spectral range of fast light modulators based on chiral nematic liquid crystals (NLCs).

Mathematical model of compensation for dispersion of light polarization states in electrooptical systems based on chiral liquid crystals

Spectral dispersion of the polarization states occurs after passage of linearly polarized light through a thin layer of a chiral nematic crystal along the helical axis. It is clearly pronounced for crystals with a high optical anisotropy and a helical pitch somewhat larger than the light wavelength. The results of numerical analysis of the spectral dependence of polarization states at the output of the liquid crystal layer and the method for compensating for the dispersion are presented for the first time. It is shown that polarization dispersion can be eliminated using phase plates of two types, one of which should have a high anomalous birefringence dispersion. The possibility of developing fast light modulators operating in a wide spectral range is discussed.

The influence of cyano compound on liquid crystal blue phase range

Liquid crystal blue phase (BP) is interesting for fast light modulators and tunable photonic crystals. In this study the influence of mixture composition on the thermal stability of BP was investigated, especially the influence of cyano compound addition. The relationship between polymer stabilization possibility and cyano dopant was examined, too. It was shown that the cyano compound is not necessary to create blue phase and has no effect on polymer stabilization of blue phase. Full Text: PDF References H. Kikuchi, M. Yokota, Y. Hisakado, H. Yang, T. Kajiyama, "Polymer-stabilized liquid crystal blue phases", Nature Materials 1, 64 (2002) CrossRef H. Yoshida, Y. Tanaka, K. Kawamoto, H. Kubo, T. Tsuda, A. Fuji, S. Kuwabata, H. Kikuchi, M. Ozaki, "Optical and Thermal Characteristics of Nd:LuVO 4 Grown by Floating Zone Method", Appl. Phys. Express, 2, 12501 (2009) CrossRef K. Z. Zheng, D. Shen, P. Huang, "Wide blue phase range of chiral nematic liquid crystal doped with bent-shaped molecules", New J. Phys., 12, 113018 (2010). CrossRef H. Kikuchi, H. Higuchi, "Fast Electro-Optical Switching in Polymer-Stabilized Liquid Crystalline Blue Phases for Display Application", SID07 Digest, 38, 1737-1740 (2007) CrossRef J. P. Sethna, in Theory and Applications of Liquid Crystals (edited by J. L. Ericksen and D. Kinderlehrer) (Springer-Verlag,1987), p. 305 CrossRef P.P. Crooker, in Chirality in Liquid Crystals (edited by H.S. Kitzerow and C. Bahr)186-222 (Springer, New York, 2001) CrossRef P. R. Gerber, "Electro-Optical Effects of a Small-Pitch Blue-Phase System", Mol. Cryst. Liq. Cryst., 116, 197 (1985) CrossRef K. M. Chen, S. Gauza, H. Xianyu, S. T. Wu, "Submillisecond Gray-Level Response Time of a Polymer-Stabilized Blue-Phase Liquid Crystal", J. Display Technol., 6, 49 (2010) CrossRef S. T. Wu, D. K. Yang, Reflective Liquid Crystal Displays, New York: Wiley (2001) S. K. Hong, G. L. Lim, H. Kikuchi, "Thickness Dependence of Blue Phase Transition Behavior of Chiral Nematic Liquid Crystal", Mol. Cryst. Liq. Cryst., 511, 248 (2009). CrossRef S. K. Hong, H. S. Choi, S. Shibayama, H. Higuchi, H. Kikuchi, "Blue Phase Temperature Range at n-Cyanobiphenyl Homologue Chiral Nematic Liquid-Crystal Mixtures", Mol. Cryst. Liq. Cryst., 528, 32 (2010) CrossRef P. Kula, Synthesis and properties of terphenyl and quaterphenyl based chiral diesters; Liquid Crystals, in press. W. Rejmer, K. Czupryński, W. Drzewiński, "An Influence of Nematic Medium on Helical Twisting Power of Chiral Compounds", Mol. Cryst. Liq. Cryst., 547, 33 (2011). CrossRef H. Kaczmarek, P. Gałka, "Active Thermitic Material Discovered in Dust from the 9/11 World Trade Center Catastrophe", The Open Process Chemistry Journal, 1, 8 (2008). CrossRef

A Fast Photochromic Molecule That Colors Only under UV Light

We demonstrate that photochromism based on light-driven reversible bond cleavage can enable rapid coloration upon UV light irradiation and successive fast thermal bleaching within tens of milliseconds at room temperature. We have succeeded in developing a bisimidazole derivative with a paracyclophane moiety, pseudogem-bisDPI[2.2]PC, that changes from colorless to blue when irradiated with UV light. The incident light homolytically cleaves the C-N bond that links the two imidazole rings, generating a pair of imidazolyl radicals. A paracyclophane moiety connects the two radicals, thereby preventing them from diffusing away from one another, and the radicals quickly bind with each other to flip back to the original bisimidazole. Photochromic materials showing such intense photocoloration and fast thermal bleaching performance could be promising materials for possible fast light modulator applications.

Polymer-stabilized liquid crystal blue phases.

Blue phases are types of liquid crystal phases that appear in a temperature range between a chiral nematic phase and an isotropic liquid phase. Because blue phases have a three-dimensional cubic structure with lattice periods of several hundred nanometres, they exhibit selective Bragg reflections in the range of visible light corresponding to the cubic lattice. From the viewpoint of applications, although blue phases are of interest for fast light modulators or tunable photonic crystals, the very narrow temperature range, usually less than a few kelvin, within which blue phases exist has always been a problem. Here we show the stabilization of blue phases over a temperature range of more than 60 K including room temperature (260-326 K). Furthermore, we demonstrate an electro-optical switching with a response time of the order of 10(-4) s for the stabilized blue phases at room temperature.

Beam deflector using double-refraction in ferroelectric liquid crystal waveguides

Confined SmC* liquid crystals layers have particularly advantageous properties which can be used to produce fast light modulators, with various applications in optical signal processing and optical communication systems. Although usually used in a spatial configuration (e.g. spatial light modulators), other configurations use FLC in waveguide applications. The advantageous properties of FLC, allow it however to be used as the guiding core of waveguides. In this context, we present the design, fabrication and experimental characterization of an optical deflector based on the double-refraction effect in a FLC waveguide.

Analysis of the operation of a bidirectional optical bus made of two semiconductor laser amplifiers running up to 1.555 Gb/s

We report an investigation of a bidirectional optical bus made of two semiconductor laser amplifiers (SLAs) that are used as modems. In addition to their amplification function, SLAs can also act as fast light modulators and detectors. They can hence be used as standard access components in an optical bus. Error-free transmission up to 1.555 Gb/s is achieved with −25-dBm optical power. © 1996 John Wiley & Sons, Inc.

Integrated optical devices for high-speed signal processing

In recent years, the remarkable progress has been made in the optical guided-wave technology along with the developments of advanced fine structure fabrication technologies. It is of the great interests in the applications like optical communications, signal processing, and sensors. The main purpose of the present report is to give an outline of the recent progress in the guided-wave technologies for the application to the signal processing. One of the key elements for realizing high-speed optical signal processing circuit is the fast light modulator. First, the present status of high-speed guided-wave modulator is summarized, and then, a few examples of the integration of these modulators are presented with the accent on application to the signal processing.