Spatially resolved phase objects using Mach–Zehnder interferometry

Phase characterization with a good spatial resolution is crucial for focused beams in nonlinear media. The phase-shifting interferometry technique, using the least-squares error criterion for several interferograms, is implemented using a reflective spatial light modulator (SLM). The method provides a convenient calibration for any phase-shift steps. The reliability of the proposed method is checked by direct comparison with results obtained by the Fourier transform method as well as using a previously characterized circular phase object

D4σ nonlinear measurement inside a 4f-Z-scan system

The D4σ method using a 4f-Z-scan system is presented in order to increase the sensitivity and the resolution in Z-scan measurements. The numerical calculations and the experimental results validate our approach

Nonlinear characterization of materials using the D4σ method inside a Z-scan 4f-system

We show that direct measurement of the beam radius in Z-scan experiments using a CCD camera at the output of a 4f -imaging system allows higher sensitivity and better accuracy than Baryscan. One of the advantages is to be insensitive to pointing instability of pulsed lasers because no hard (physical) aperture is employed as in the usual Z-scan. In addition, the numerical calculations involved here and the measurement of the beam radius are simplified since we do not measure the transmittance through an aperture and it is not subject to mathematical artifacts related to a normalization process, especially when the diffracted light intensity is very low

All-Dielectric Rod-Type Metamaterials at Optical Frequencies

Light propagation in all-dielectric rod-type metamaterials is studied theoretically. The electric and magnetic dipole moments of the rods are derived analytically in the long-wavelength limit. The effective permittivity and permeability of a square lattice of rods are calculated by homogenizing the corresponding array of dipoles. The role of dipole resonances in the optical properties of the rod array is interpreted. This structure is found to exhibit a true left-handed behavior, confirming previous experiments [L. Peng \textit{et al.}, Phys. Rev. Lett. \textbf{98}, 157403 (2007)]. A scaling analysis shows that this effect holds at optical frequencies and can be obtained by using rods made, for example, of silicon.Comment: 10 pages, 4 figures. The title has been shortened; Figs. 1, 2 and 3 have been modified; Eq. 4 has been corrected (sign error); A few sentences have been added/rewritte

Measurement of the third order optical nonlinearities of graphene quantum dots in water at 355 nm, 532 nm and 1064 nm

The nonlinear responses of the suspension of graphene quantum dots (GQDs) in water are investigated at 355 nm, 532 nm and 1064 nm in the picosecond regime. The third-order nonlinear (NL) refractive index and the NL absorption coefficients are determined. We found that only under UV illumination is the NL response large. Furthermore, the NL refractive index and the saturable absorption are estimated for a single nanoparticle constituting the GQDs through a simple model. The obtained value of the Kerr coefficient is in the order of magnitude of that found in bulk materials and three orders of magnitude lower with an opposite sign than that found for the monolayer graphene

Measurements of the third- and fifth-order optical nonlinearities of water at 532 and 1064 nm using the D4σ method

The nonlinear response of liquid water was investigated at 1064 and 532 nm using a Nd:YAG laser delivering pulses of 17 ps and its second harmonic. The experiments were performed using the D4σ method combined with the Z-scan technique. Nonlinear refractive indices of third- and fifth-order were determined, as well as the three-photon absorption coefficient, for both wavelengths. A good agreement was found between theory and experiment

pH prediction in concentrated aqueous solutions under high pressure of acid gases and high temperature

International audienceAn extended model for pH prediction in oil and gas environments has been developed. Accurate pH calculations for high pressure and high temperature applications depends mainly on CO2 and H2S partial pressures, the ionic strength, the chemical composition of the solution, and the temperature. Accounting for the non-ideal behaviors of liquid and gas phases allows pH calculations up to 200 °C, 2000 bar total pressure, and ionic strengths up to 5 mol.L-1. The results are consistent with experimental measurements and with other models reported in the literature

Degenerate multiwave mixing using Z-scan technique

This study deals with a multiwave mixing experiment using Z-scan technique. We show that it is possible to simplify the complex degenerate four-wave mixing(DFWM) experimental setup in order to characterize nonlinear materials. One object composed of three circular apertures is used as an input in a 4 f coherent imaging system. When the nonlinear material is moved around the focus, we observe the variations of the forward fourth wave at the output as well as other diffracted waves. Experimental and simulated images are presented here to validate our approach. We show also that this method increases significantly the sensitivity of the measurement compared to DFWM. We provide a simple quadratic relation that allows the characterization of the cubic optical nonlinearity

Investigation of the third-order nonlinear optical properties in porphyrin solutions in the picosecond regime

The D4σ-Z-scan technique is used to evaluate the sign and the magnitude of the nonlinear (NL) refractive index and the NL absorption (NLA) coefficient with a laser delivering single pulses in the picosecond regime at 355 nm, 532 nm and 1064 nm. The NL optical response of the zinc porphyrins (Pph) has been found to be significantly enhanced. The study of the NLA and refraction is performed, taking into account the time dependence and the spectral width of the incident laser. The variations of the NL coefficients as a function of the intensity and the concentration are provided and are found to be linear