Components Of Third-order Susceptibility Research Articles

Power-dependent nonlinear optical behaviours of ponceau BS chromophore at 532 nm via Z-scan technique

This paper reports on the power-dependent nonlinear optical (NLO) attributes for both nonlinear refractive index, n2 and nonlinear absorption coefficient, β of Ponceau BS (PBS) chromophore, a synthetic organic compound that falls under azo family. Single-beam Z-scan technique was utilized for the nonlinear measurement. Dominant absorption peak is observed in the visible region due to the high conjugation of diazene functional group absorption. The existence of vital vibrational bonds e.g. the azo bond (1576 cm−1) was confirmed via Fourier Transform Infrared Spectroscopy (FTIR). The intermolecular charge transfer (ICT) of delocalized electrons is responsible for the quick nonlinear response of the sample under intense laser excitation. Response from the closed and open aperture Z-scan technique indicates that PBS chromophore exhibits self-defocusing effects with negative sign of n2 and reverse saturable absorption (RSA) in the order of 10−9 and 10−4 respectively. The real and imaginary components of third order susceptibility, χ3 are relatively high in the order of 10−8 and 10-5 respectively under different laser powers (0.12, 0.14, 0.16, 0.18 & 0.20 W). In short, PBS chromophore shows promising features and can be considered as a potential candidate for various NLO applications under low-power laser operation.

Nonlinear absorption properties of ZnO and Al doped ZnO thin films under continuous and pulsed modes of operations

In the present investigation, we present the variations in nonlinear optical (NLO) properties of undoped and Al doped ZnO (AZO) films under two different off-resonant regimes using continuous and pulsed mode lasers. Z-scan open aperture experiment is performed to quantify nonlinear absorption constant and imaginary component of third order susceptibility. Reverse saturable absorption (RSA) and saturable absorption (SA) behaviors are noticed in both undoped and AZO films under pulsed mode and continuous wavelength (CW) regime respectively. The RSA and SA behavior observed in the films are attributed to two photon absorption (TPA) and thermal lensing properties respectively. The thermal lensing is assisted by the thermo-optic effects within the films due to the continuous illumination of the laser.

Interferometric assessment of induced nonlinear susceptibility in perturbed single-mode optical fiber for all-optical switching

The induced variations of complex third-order susceptibilities in bent single-mode fiber at the standard operating wavelengths, 1300 and 1550 nm, is studied using Fizeau interferometry for radius of curvature ranges from 5 to 11 mm. At λ = 1300 nm and at the minimum radius of curvature R = 5 mm, the cladding real (dispersive) third-order susceptibility Re|χ(3)| = 1.167×10−15±0.8% electrostatic unit (esu) on the tensile side, whereas on the compressed side it is 1.309×10−15 esu. On the tensile side, the cladding imaginary (absorptive) third-order susceptibility Im|χ(3)| = 2.089×10−18±0.8% esu, whereas on the compressed side it is 2.118×10-18 esu. For λ = 1550 nm, the cladding Re|χ(3)| and Im|χ(3)| on the tensile side are 1.116×10-15 esu and 2.478×10-18 esu, whereas on the compressed cladding side they are 1.259×10-15 esu and 2.514×10-18 esu, respectively. At λ = 1300 nm and R = 5 mm, the core Re|χ(3)| is given by 1.318×10-15 esu on the tensile side and 1.324×10-15 esu on the compressed side. The asymmetry in Im|χ(3)| is given by 4.687×10-17 esu on the tensile side and by 4.89×10-17 esu on the compressed side. With λ = 1550 nm, the core Re|χ(3)| asymmetry is given by 1.267×10-15 esu on the tensile side and by 1.272×10-15 esu on the compressed side. For Im|χ(3)| its core asymmetry is provided by 5.561×10-17 esu on the tensile side and by 5.564×10-17 esu on the compressed side. The observed asymmetry in the measured complex third-order susceptibility components for bent fibers is attributed to the nonlinear response of Young's modulus of fiber material.

Modified elliptically polarized light Z-scan method for studying third-order nonlinear susceptibility components

The normal elliptically polarized light Z-scan method is modified by adding a quarter-wave plate and an analyzer before the detector. The normalized transmittance formulas of modified elliptically polarized light Z-scan are obtained for media with negligible nonlinear absorption. Compared with normal linearly and elliptically polarized light Z-scan methods, an increase of sensitivity by a factor of larger than 4 is achieved for the real part of third-order susceptibility component's measurements using this modified elliptically polarized light Z-scan method. The analytical results are verified by studying the real part of independent susceptibility components of CS(2) liquid. Moreover, the potential application for cross-polarized wave generation is discussed.