41 research outputs found
Spatially incoherent modulational instability in a non local medium
We investigate one-dimensional transverse modulational instability in a non
local medium excited with a spatially incoherent source. Employing undoped
nematic liquid crystals in a planar pre-tilted configuration, we investigate
the role of the spectral broadening induced by incoherence in conjunction with
the spatially non local molecular reorientation. The phenomenon is modeled
using the Wigner transform.Comment: 13 pages with 4 figures included. To be published in Laser Physics
Letter
Nonlinear Optical Effects in Nematic LiquidâCrystal Films in the 1.55 mm Spectral Region
We have studied the optical nonlinearities of nematic liquid crystals in the near IR communication spectral region [1.55 ”m]. The origins of the refractive index changes are thermal indexing effect and director axis reorientations. Very large refractive index and phase modulation of several ?'s can be generated with mW laser power in micron thick dye-doped nematic liquid crystal films
Laser-induced nonlinear thermal orientation effects in planar and homeotropic nematic liquid crystals
Optical Holographic Grating Formation in Dye- and Fullerene-Doped Liquid Crystalline System
The nonlinear optical properties of nematic liquid crystal films doped with dyes of fullerene C60 are studied. Nematic liquid crystals were doped with azo-dyes, and tested for their optical storage capabilities. An electro-optical holographic storage grating effect is observed in C60-doped nematic liquid crystal films. The effect is attributed to molecular axis reorientation caused by the combination of an applied DC field and an optically induced DC space charge. The observed nonlinear sensitivity of the films is larger than that of other materials studied
Dye-doped Photorefractive Liquid Crystals for Dynamic and Storage Holographic Grating Formation and Spatial Light Modulation
The basic mechanisms of photo-induced space charge field formation, director axis re-orientation, and refractive index changes in fullerene C60- and dye-doped nematic liquid crystals films are presented. In particular, in aligned methyl-red-doped nematic liquid crystal film, we observe a nonlinear index change coefficient as high as 10 cm2/W, associated with purely optically induced liquid crystal director axis re-orientation. Experimental observations of dynamic and high-resolution storage holographic grating formation, two beam coupling with gain of nearly 3000 cm-1, optical limiting action at nanowatt cw laser power, and incoherent-coherent image conversion at ÎŒW/cm2 light intensity level are discussed