Third order optical non–linearities of nematic liquid crystals

Li, L.; Yuan, H.; Hu, Gongjian; Palffy‐Muhoray, Peter

doi:10.1080/02678299408036542

Cited by 44 publications

(15 citation statements)

References 6 publications

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“…This presence of a CW power pedestal [5,27] would affect the time-average excitation properties, however, narrow dark solitons can be excited on top of pulses with a large dispersion length compared to the notch waist , [29,30] enabling the independent control of the average power and the realization of anti-bullets under experimentally feasible conditions. An…”

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confidence: 99%

Accessible Light Bullets via Synergetic Nonlinearities

et al. 2009

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We introduce a new form of stable spatio-temporal self-trapped optical packets stemming from the interplay of local and nonlocal nonlinearities. Pulsed self-trapped light beams in media with both electronic and molecular nonlinear responses are addressed to prove that spatial and temporal effects can be decoupled, allowing for independent tuning. We numerically demonstrate that (3+1)D light bullets and anti-bullets, i. e. bright and dark temporal solitons embedded in stable (2+1)D nonlocal spatial solitons, can be generated in reorientational media under experimentally feasible conditions.

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confidence: 99%

Accessible Light Bullets via Synergetic Nonlinearities

et al. 2009

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“…The fast electronic nonlinearity of this LC is measured in terms of the intensity dependent refractive index n 2 . For 5CB n 2,⊥ = 1.9·10 − 18 m 2 /W and n 2,|| = 2.5·10 −18 m 2 /W, these values have been measured at 532 nm for 32 ps pulses [6]. Compared to silica fibers these values are about two orders of magnitude larger (n 2,SiO2 = 2.4·10 −20 m 2 /W).…”

Section: Theorymentioning

confidence: 79%

Supercontinuum Generation in Fibers Infiltrated with Liquid Crystals

Rasmussen

Bang

Lægsgaard

et al. 2006

2006 International Conference on Transparent Optical Networks

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Supercontinuum generation in a capillary tube infiltrated with a nematic liquid crystal is investigated theoretically in the near infrared region. A liquid crystal with a high electronic nonlinearity is chosen, which makes it possible to generate 100 nm wide supercontinua using 10 ps pulses with peak power 1.5 kW in a 10 cm long waveguide. The possibility of tuning the spectrum of the generated supercontinuum by changing the dispersion of the waveguide is also considered. It is found that the broadening of the spectrum in both the normal and anomalous regime is mainly due to self phase modulation, and therefore the dispersion of the waveguide is only of minor importance. The tuning of the dispersion is achieved by varying the temperature of the liquid crystal inside the capillary. Keywords: nonlinear optics, liquid crystals, supercontinuum generation. INTRODUCTIONRecently the possibility of making tunable optical devices based on liquid crystals (LCs) has attracted much attention [1]. Such devices can be realized, because the optical properties of LCs can be varied by changing the temperature or applying an external electric field. Together with the unique properties of photonic crystal fibers (PCFs) such as endlessly singlemode, and zero dispersion wavelengths in the visible spectrum, optical devices based on PCFs and LCs hold ongoing promise for potential applications in photonics. Along with these tunable properties, LCs also possess high nonlinearities. When using LCs in nonlinear optics it is often the reorientational nonlinearity of the LC that is being exploited, since this nonlinearity can be several orders of magnitude larger than in silica [2]. But since the time it takes to reorient the LC molecules is of the order of microseconds it cannot be used for supercontinuum generation (SCG) with short pulses, where the pulses are of the order of picoseconds or femtoseconds. For such short pulses it is the fast electronic nonlinearity of the material that is responsible for SCG. It turns out that this fast electronic nonlinearity for many LCs is about two orders of magnitude larger than in silica. Often SCG has been considered at visible wavelengths, which can be used for optical coherence tomography. But also at the telecommunication wavelengths around 1550 nm SCG also has possible applications, since it can be used to produce short pulses at multiple wavelengths simultaneously, which can be used for WDM communication systems [3].In the present work we propose a supercontinuum light source in the near infrared spectrum consisting of a capillary silica tube infiltrated with LC. The high electronic nonlinearity of the LC allows us to generate 100nm wide spectra from 10 ps pulses with peak power 1.5 kW. The temperature dependence of the refractive index of the LC allows us to change the dispersion profile of the device, and thereby investigate how the generated spectra are modified.

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“…Studies of the nonlinear scattering show that it is also nearly temperature independent [26] and inversely proportional to the square of the beam wavelength, i. e., proportional to λ −2 [27]. A similar study of a planar oriented sample of 5CB [10], using the λ = 514.5 nm line of an argon laser at comparable power, showed no nonlinear optical absorption, either in the nematic phase or close to the N-I transition.…”

Section: Resultsmentioning

confidence: 99%

“…The critical exponent seems to corroborate the tri-critical character of this phase transition. Previously, Li et al [10] had shown that the optical absorption of a pure sample of 5CB under ms-pulses of a λ = 514 nm cw laser is linear at the nematic side of the N-I transition, i. e., β ,⊥ = 0 . Although multiphoton absorption processes are usually observed under intense pulsed laser irradiation, there are many reports on the observation of two-photon absorption under irradiation of middle or low power cw lasers in highly absorbing dye-doped liquid crystal, as consequence of a two-photon absorption process [11,12,13,14] or to reorientation of the nematic director [15].…”

Section: Introductionmentioning

confidence: 99%

Enhancement of the Nonlinear Optical Absorption of the E7 Liquid Crystal at the Nematic–Isotropic Transition

et al. 2012

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We present an experimental study of the nonlinear optical absorption of the eutectic mixture E7 at the nematic-isotropic phase transition by the Z-scan technique, under continuos-wave excitation at 532 nm. In the nematic region, the effective nonlinear optical coefficient β, which vanishes in the isotropic phase, is negative for an extraordinary beam and positive for an ordinary beam. The parameter S NL , whose definition in terms of the nonlinear absorption coefficient follows the definition of the optical-order parameter in terms of the linear dichroic ratio, behaves like an order parameter with critical exponent 0.22 ± 0.05, in good agreement with the tricritical hypothesis for the N-I transition.

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Third order optical non–linearities of nematic liquid crystals

Cited by 44 publications

References 6 publications

Accessible Light Bullets via Synergetic Nonlinearities

Accessible Light Bullets via Synergetic Nonlinearities

Supercontinuum Generation in Fibers Infiltrated with Liquid Crystals

Enhancement of the Nonlinear Optical Absorption of the E7 Liquid Crystal at the Nematic–Isotropic Transition

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