Characterisation of Photoalignment Materials for Photonic Applications at Visible and Infrared Wavelengths

Beccherelli, Romeo; Manolis, Ilias; d’Alessandro, Antonio

doi:10.1080/15421400590930971

Cited by 17 publications

(9 citation statements)

References 15 publications

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“…After modal analysis, it results that propagation is only compatible with an effective pretilt in the 15 to 24 range [24]. This is quite higher than the 1.3 pretilt we usually obtained for E7 in antiparallel glass cells when evaluated with the crystal rotation method [25].…”

Section: Effect Of Molecular Director Distributionmentioning

confidence: 95%

Integrated Optics Devices Based on Liquid Crystals

Beccherelli

Bellini

Donisi

et al. 2007

Molecular Crystals and Liquid Crystals

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We describe the technology behind a platform for integrated optics based on liquid crystals. Design and technological issues are addressed and effective technological solutions are presented. The physical implementation of optical waveguides characterized by a practical and reproducible process based on preferential etching of crystalline silicon substrates are presented. Devices are manufactured by wet etching a Si substrates first and then by thermally growing thick SiO 2 cladding layer. A nematic liquid crystal is used as core of the waveguiding devices. Experimental results on polarizing properties and single mode propagation of infrared light are presented and discussed.

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Section: Effect Of Molecular Director Distributionmentioning

confidence: 95%

Integrated Optics Devices Based on Liquid Crystals

Beccherelli

Bellini

Donisi

et al. 2007

Molecular Crystals and Liquid Crystals

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“…2(a), in particular when photo-alignment techniques 24,31 or well-developed vacuum-based SiO x deposition techniques are employed; and (iv) the external electric field distortion is lower than in the vertical wall case, therefore the LC molecules are more efficiently reoriented.…”

Section: Optical Structurementioning

confidence: 99%

Tunable one-dimensional photonic crystal slabs

et al. 2007

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A 1D photonic crystal slab based on preferential etching of commercially available silicon-on-insulator wafers is presented. Compared to dry etching, anisotropic wet etching is more tolerant to errors as it is self-stopping on crystallographic {111} planes and it produces a more precise geometry with symmetries and homothetic properties, with surface roughness close to 1 nm. The resulting grooves are infiltrated by low viscosity liquid crystal having large positive optical anisotropy. The use of slanted grooves provides advantages: first of all the complete filling of slanted grooves is simplified when compared to vertical walls structures. Furthermore alignment is significantly facilitated. Indeed the liquid crystal molecules tend to align with their long axis along the submicron grooves. Therefore by forcing reorientation out of a rest position, the liquid crystal presents a choice of refractive indices to the propagating optical field. The liquid crystal behavior is simulated by a finite element method, and coupled to a finite difference time domain method. We investigate different photonic crystal configurations. Large tunability of bandgap edge for TE polarization is demonstrated when switching the liquid crystal with an applied voltage. We have also studied the use of the same device geometry as a very compact microfluidic refractometric sensor.

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“…This is in contrast to the usual rubbing performed by a machine on both inner sides of substrates as conventionally used for planar LC devices. Better alignment uniformity and lower scattering are expected from the use of either a mechanically controlled rubbing machine or contact free photoalignment techniques 42,43 . Both solutions are being tested and will be adopted for the next samples.…”

Section: Linear Optical Transmissionmentioning

confidence: 99%

Nonlinear switching of near infrared light in liquid crystal on silicon channel waveguides

et al. 2010

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This paper reports on linear and nonlinear optical properties of channel waveguides made of micromachined SiO2/Si V-grooves filled with nematic liquid crystal E7. Experiments demonstrate operation of the waveguides in the C-band (1530 - 1565 nm). Molecular reorientation of the NLC, induced either by an applied low frequency electric field or by the electric field of the light itself, changes the LC refractive index distribution then allowing the control of guided light. Design criteria and techniques of channel waveguides for both electro-optical and all-optical switching and modulation will be discussed. Experiments are presented where it is showed that light at 1550 nm, fiber-coupled to the LC waveguide is optically modulated by an optical beam with an input power below 25 mW. All-optical switching of a signal at 1510 nm with a contrast over 10 dB is also demonstrated by using a copropagating control signal at 1560 nm. A model of the waveguide is also presented able to explain linear and nonlinear experimental results

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Characterisation of Photoalignment Materials for Photonic Applications at Visible and Infrared Wavelengths

Abstract: In this paper we discuss the processing and characterisation of Linearly Polymerisable Polymers to align Liquid Crystal Prepolymers for use in photonic application. Preliminary results on uniform retardation waveplates for use in free space optics are given.

Cited by 17 publications

References 15 publications

Integrated Optics Devices Based on Liquid Crystals

Integrated Optics Devices Based on Liquid Crystals

Tunable one-dimensional photonic crystal slabs

Nonlinear switching of near infrared light in liquid crystal on silicon channel waveguides

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