scholarly journals Switchable Photonic Nanojet by Electro-Switching Nematic Liquid Crystals

Nanomaterials ◽  
2019 ◽  
Vol 9 (1) ◽  
pp. 72 ◽  
Author(s):  
Bintao Du ◽  
Jun Xia ◽  
Jun Wu ◽  
Jian Zhao ◽  
Hao Zhang
Keyword(s):  
Refractive Index ◽  
Liquid Crystals ◽  
Double Layer ◽  
Nematic Liquid Crystals ◽  
Surrounding Medium ◽  
Refractive Index Change ◽  
Electric Energy ◽  
Incident Wavelength ◽  
Photonic Nanojet ◽  
Energy Focusing

This paper first presents a switchable photonic nanojet (PNJ) generated by a polystyrene (PS) microsphere immersed in nematic liquid crystals (NLCs). The PNJ is switched by applying external voltage, which originates from the refractive index change in the surrounding medium caused by the field-induced realignment of liquid crystal molecules. By tuning the refractive index of NLCs larger or smaller than that of the PS microsphere, the PNJ can be switched off or on. Moreover, we present an optimization study to seek a better electric energy focusing property of the PNJ. Our results reveal that the switchability of PNJ can be optimized by applying a shorter incident wavelength, a double-layer microsphere, and a PS ellipsoid. The full width at half-maximum (FWHM) generated by the PS ellipsoid is narrower than that generated by the microsphere with a shorter incident wavelength. The intensity contrast of the PS ellipsoid is higher than that of the double-layer microsphere. As a whole, the switchability of PNJ can be best optimized by a PS ellipsoid. This should open the way for the development of integrated photonic devices.

ANALYSIS OF OPTICALLY INDUCED REFRACTIVE INDEX CHANGE OF DYE-DOPED NEMATIC LIQUID CRYSTALS

2002 ◽  
Vol 11 (01) ◽  
pp. 1-12 ◽  
Author(s):  
A. SHISHIDO ◽  
M.-Y. SHIH ◽  
I. C. KHOO
Keyword(s):  
Refractive Index ◽  
Liquid Crystals ◽  
Diffraction Efficiency ◽  
Order Parameter ◽  
Nematic Liquid Crystals ◽  
Refractive Index Change ◽  
Beam Polarization ◽  
Methyl Red ◽  
Parameter Modification ◽  
Index Changes

We present a detailed quantitative experimental and theoretical study of laser induced refractive index changes in nematic liquid crystals doped with methyl-red, disperse red and azobenzene liquid crystal. These refractive index changes, originating from molecular reorientations and order parameter modification, are measured by means of intensity and polarization grating methods. The reorientation of the director axis is calculated from polarization dependence of the probe beam diffraction efficiency. The contribution of each effect to the total diffraction efficiency is quantitatively evaluated. In general, we found that the reorientational direction of the NLC molecules depends on the dopants as well as the nature of the pump beam polarization state. In methyl-red doped samples, the laser induced reorientation mechanism dominates, whereas order parameter modification plays a major role in the others.

Nonlinear effects in photonic crystal fibers filled with nematic liquid crystals

Open Physics ◽  
2008 ◽  
Vol 6 (3) ◽  
Author(s):  
Urszula Laudyn ◽  
Katarzyna Rutkowska ◽  
Robert Rutkowski ◽  
Mirosław Karpierz ◽  
Tomasz Woliński ◽  
...  
Keyword(s):  
Refractive Index ◽  
Liquid Crystals ◽  
Photonic Crystal ◽  
Low Power ◽  
Light Beam ◽  
Photonic Crystal Fibers ◽  
Nematic Liquid Crystals ◽  
Nonlinear Effects ◽  
The Creation ◽  
Crystal Fibers

AbstractWe have investigated the nonlinear propagation of light in photonic crystal fibers filled with nematic liquid crystals. We analyzed a configuration with a periodic modulation of the refractive index corresponding to a matrix of waveguides. Matrices of coupled waveguides allow observing a variety of new phenomena both for low power light beam propagation and with an existence of nonlinear effects. The opportunity for the creation of solitary waves caused by the interplay between diffraction and nonlinear effects in these kinds of fibers is investigated. At low power the propagating light beam spreads as it couples to more and more waveguides. When the intensity is increased the light modifies the refractive index distribution, inducing a defect in the periodic structure. The creation of such a defect can lead to a situation in which the light becomes self-localized and its diffractive broadening is eliminated. Eventually, in the case of positive Kerr-type nonlinearity, a discrete soliton can be created. In the case of negative nonlinearity the refractive index decreases with the optical power and can lead to bandgap shifting. The incident beam, with a frequency initially within the bandgap, is then turned outside the bandgap resulting in the changing of the propagation effect for the discrete diffraction effect. As a consequence the delocalization of the light can be observed.

High Polaried Transmission Effects for Double-Layer Metallic Grating Films on GaN Substrate

2011 ◽  
Vol 295-297 ◽  
pp. 1289-1293
Author(s):  
Bing Cao ◽  
Gui Ju Zhang ◽  
Qin Han ◽  
Chin Hua Wang ◽  
Jian Feng Wang ◽  
...  
Keyword(s):  
Refractive Index ◽  
Double Layer ◽  
Transition Layer ◽  
Light Transmission ◽  
Light Emitting Diode ◽  
Extinction Ratio ◽  
Polarized Light ◽  
Incident Wavelength ◽  
Metallic Grating ◽  
Low Refractive Index

Highly polarized light transmission from GaN based light emitting diode is proposed using a double-layer metallic grating film and a dielectric transition layer. TM mode transmission and the polarized extinction ratio (ER) are calculated using commercial software, based on a full vector implementation of Rigorous Coupled Wave Analysis (RCWA) algorithm. Such a thin-film double-layer grating with subwavelength metallic stripes are designed and simulated by perfect parameters of period, thickness and filling factor for achieving good polarization properties. It is found that TM transmission and ER are almost stable and flat under different slit arrays of the double-layer grating. The polarized structure shows larger width of incident wavelength with a transition layer of a low refractive index than that of a high refractive index, but higher TM transmission and ER can be obtained for low refractive index transition layer. Flat sensitivity and high transmission of the TM mode on the double-layer metal grating thickness have been achieved. Up to 100nm range of the grating height can be employed to achieve TM transmission more than 92% while ER> 20dB. The results provide guidance in designing, optimizing and fabricating the integrated GaN-based and polarized photonic devices.

scholarly journals Voltage-Controllable Guided Propagation in Nematic Liquid Crystals

2018 ◽  
Vol 2018 ◽  
pp. 1-4
Author(s):  
Hsin-Yu Yao ◽  
Shang-Min Yeh
Keyword(s):  
Refractive Index ◽  
Liquid Crystals ◽  
Single Channel ◽  
Coupling Effect ◽  
Nematic Liquid Crystals ◽  
The Self ◽  
External Voltage ◽  
Self Focusing ◽  
Guided Propagation ◽  
Adjacent Channels

Voltage-controllable guided channels are formed in a planar nematic liquid crystals cell. The director of liquid crystals can be aligned by applying external voltage, which results in a difference of the refractive index between two adjacent channels; therefore, the incidence beam can be coupled from one channel to another. First, we discussed the propagation of the beam and the self-focusing in a single channel; then we discussed the propagation of the beam and the coupling effect in the two channels. The results showed that the propagation of the beam can be selected in each channel by applying voltages in the two individual electrode channels.

scholarly journals Refraction of nonlinear beams by localized refractive index changes in nematic liquid crystals

2010 ◽  
Vol 82 (5) ◽  
Author(s):  
Gaetano Assanto ◽  
Antonmaria A. Minzoni ◽  
Noel F. Smyth ◽  
Annette L. Worthy
Keyword(s):  
Refractive Index ◽  
Liquid Crystals ◽  
Nematic Liquid Crystals ◽  
Nonlinear Beams ◽  
Index Changes

Effects of Cell Parameters on Photothermal Refractive Index Change in Guest Host Liquid Crystals

2000 ◽  
Vol 39 (Part 1, No. 11) ◽  
pp. 6376-6382 ◽  
Author(s):  
Hiroshi Ono ◽  
Yoshiro Harato ◽  
Junichi Kikuhara
Keyword(s):  
Refractive Index ◽  
Liquid Crystals ◽  
Refractive Index Change ◽  
Index Change ◽  
Cell Parameters

Mirrorless lasing from nematic liquid crystals in the plane waveguide geometry without refractive index or gain modulation

2006 ◽  
Vol 89 (3) ◽  
pp. 031114 ◽  
Author(s):  
L. M. Blinov ◽  
G. Cipparrone ◽  
P. Pagliusi ◽  
V. V. Lazarev ◽  
S. P. Palto
Keyword(s):  
Refractive Index ◽  
Liquid Crystals ◽  
Nematic Liquid Crystals ◽  
Plane Waveguide ◽  
Gain Modulation ◽  
Waveguide Geometry
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