Characterization of Optical Nonlinearity in Dye-Doped Nematic Liquid Crystal and the Effect of AC Voltage on Its Behavior

Mousavi, S.H.; Ara, M.H. Majles; Soheilian, F.; Koushki, E.; Salmani, S.; Bahramian, R.

doi:10.1080/15421400802218736

Cited by 3 publications

(7 citation statements)

References 8 publications

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“…98. The measurements reveal that the molecular reorientation of the LCs that is induced by the photoisomerization of the azo dyes dominates at low red-light intensity, but the thermal effect compensates for the molecular reorientational nonlinearity of the sample at high red-light intensity.…”

Section: Molecular Reorientation Effectmentioning

confidence: 90%

“…Therefore, the variation in the nonlinear refractive index n 2 with additional irradiation with green light is believed to be caused by the thermal effect, which can be understood by the temperature-dependent refractive index of a nematic LC. 98 When the green-beam intensity reached a critical value, such that the temperature of the irradiated spot equals or exceeds the clearing temperature T C , the Z-scan curve became a horizontal straight line, which meant n 2 = 0, as the cross-dot curve shown in Fig. 14. …”

Section: Thermal Effectmentioning

confidence: 99%

“…98. Figure 12 presents the experimental setup, where a linearly polarized red He-Ne laser was focused in the z-direction onto the azo-dye (DR1)-doped LC (E7) sample aligned homogeneously.…”

Section: Thermal Effectmentioning

confidence: 99%

“…The cause is attributed to the thermal effect, which compensates for the molecular reorientation nonlinearity of the sample at high red-light intensity. 69,98 The measurement of the average temperature was done to verify the thermal effect, which contributed a defocusing increasing with I RL .…”

Section: Molecular Reorientation Effectmentioning

confidence: 99%

“…In the previous section, the reader was introduced to the fact that the thermal effect enhances n 2 of ADDLC film with the LC director parallel to the polarizations of the two pumping lasers reported in Ref. 98. The experiment with the LC director (n) perpendicular to the polarizations (P ) of the two pumping lasers was also carried out.…”

Section: Polarization Effectmentioning

confidence: 99%

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Z-Scan Measurements of Optical Nonlinearities of Dye-Doped Liquid Crystals

Lin

Fuh

2009

J. Nonlinear Optic. Phys. Mat.

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Nematic liquid crystal (NLC) is a material that features a large nonlinear optical response. The nonlinearity can be enhanced by doping a dye agent into a NLC host. In this paper, we review the nonlinear phenomena recently observed for dye-doped liquid crystal (DDLC) films measured using the Z-scan technique, which is a simple, yet powerful method for measuring nonlinear refractive indices (optical Kerr constant) n 2 and nonlinear absorption coefficients β. The nonlinear effects of liquid crystals (LCs) include the electronic polarization effect, electrostriction effect, thermal effect and reorientation effect. When LCs are doped with dye agents, the dye-induced orientational effect, photoisomerization effect, and light-induced thermal effect come about to enhance LC nonlinearity. The dominant effect depends strongly upon the spatial, temporal and polarization properties of the excitation laser beam. Generally speaking, the nonlinear effects resulted from the electronic polarization and photoisomerization effects arise from a laser pulse on picosecond duration scale, while electrostriction, thermal and reorientation effects occur on nanosecond ∼ microsecond, nanosecond ∼ millisecond and millisecond ∼ second duration scales, respectively. In this paper, the causation of nonlinear refractive index n 2 into various different experimental conditions is summarized, including the changes of the external electric field, external optical field, polarization of pump beam, temperature and the use of deuterated materials. The mechanisms, which influence the nonlinear effect in dye-doped liquid crystal films, are also discussed.

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Section: Molecular Reorientation Effectmentioning

confidence: 90%

Section: Thermal Effectmentioning

confidence: 99%

“…98. Figure 12 presents the experimental setup, where a linearly polarized red He-Ne laser was focused in the z-direction onto the azo-dye (DR1)-doped LC (E7) sample aligned homogeneously.…”

Section: Thermal Effectmentioning

confidence: 99%

Section: Molecular Reorientation Effectmentioning

confidence: 99%

Section: Polarization Effectmentioning

confidence: 99%

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Z-Scan Measurements of Optical Nonlinearities of Dye-Doped Liquid Crystals

Lin

Fuh

2009

J. Nonlinear Optic. Phys. Mat.

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Studying optical and nonlinear optical properties of synthesized azo dyes doped in polymer and liquid crystal using birefringence and Z‐ scan techniques

Nataj

Mohajerani

Nemati

et al. 2012

J of Applied Polymer Sci

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The authors report the effect of the structure of new synthesized photo-responsive azo dyes, based on N-benzyl-N-ethylaniline on their optical and nonlinear optical properties, when doped in polymer and liquid crystal (LC) hosts. Anisotropic response of dyes doped with polymer polymethyl methacrylate is studied using photo-induced birefringence experiment and the optical nonlinearity of dyes doped in LC 5CB is measured using z-scan technique. A correlation is established between dipole moment and optical/nonlinear optical response, which makes it possible to develop molecular design strategies to create structures with suitable anisotropic response and nonlinearity in various host systems for different applications. It is also shown how very little change in the structure of the dye may cause severe changes in the dipole moment and its nonlinear response.

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