<title>Switchable Bragg grating devices for telecommunications applications</title>

Abstract

Digilens is developing a new class of optical components based on the combination of Electrically Switchable Bragg Grating ( ESBG) and optical waveguide technology. One or more optical waveguides are formed on a substrate which is used as one wall of a cell filled with an ESBG. The ESBG layer forms part of the waveguide cladding, such that the grating can interact with the evanescent field of the light energy traveling in the waveguide. This device architecture has been used to make Electrical Variable Optical Attenuators with more than 50 db of controllable range, flat attenuation over the optical communications C band, fast (<100 tsecond) switching speed, and encouragingly low polarization dependent loss. Initial results on a variable wavelength-selective filter are also reported.

Engineering liquid crystals for optimal uses in optical communication systems

“…The advantage of using nano-PDLC instead of pure LC is to avoid polarization dependence due to director-privileged orientations. Various applications and industrial developments of this technique have been successfully carried out in telecommunications [73], such as variable optical attenuators and wavelength selective filters [67], as well as a planar waveguide Mach-Zehnder 262 selective switch [66]. Due to the use of nano-PDLC, ESBGbased devices have good switching speeds (v100 ms), reduced polarization dependence (when an appropriate electrode pattern is implemented) and low power consumption.…”

“…Hence attention has been paid to the fabrication of various shapes and morphologies for nano-PDLCs, and in particular to permanent gratings recorded in the bulk. This technology is based on a new family of composite electro-optic materials called holographic polymer dispersed liquid crystals (H-PDLCs) [66] and electronically switchable Bragg gratings (ESBGs) [67]. Such a nano-PDLC configuration has become one of their main applications, in particular for telecommunication uses [66].…”

“…The periodic structure vanishes with the electric field, resulting in 0th order diffraction, figure 13 (a). Under these conditions a H-PDLC is generally referred to as an electronically switchable Bragg grating (ESBG) [67]. Two main configurations are used: free-space and waveguide.…”

Reflective Display Configurations Based on Total Internal Reflection and Grating-Grating Coupling of Holographic Polymer Dispersed Liquid Crystals (H-PDLC)

“…These films are attractive for use in displays due to their high color purity, high efficiency and low cost [6]. Additionally, H-PDLC materials have been considered for use in projection display applications [7], digital camera applications [8], telecommunication applications [9], optical strain gauges [10], lasing [11,12] and photonic crystals [13][14][15][16].…”

Mesoscale Three Dimensional Lattices Formed in Polymer Dispersed Liquid Crystals: A Diamond-Like Face Centered Cubic

“…A variety of new devices using H-PDLC have been proposed, including low-power color reflective displays [5][6][7], telecommunication switches [8,9], polarization selective projection components [10], switchable lenses [11], photonic crystals [12][13][14][15][16][17], mirrorless lasing [18], laser wavelength dosimetry badges [19], optical strain gauges [20], image capture systems [21], beam steering [22], optical data storage [23,24], remote sensing [25], active U-turn switches [26], and application specific lenses [27]. There have been many basic studies on optical behavior [28][29][30][31], electro-optic switching [32], liquid crystal ordering [33], and polymer morphologies [34][35][36].…”