Various techniques to characterize the nonlinear (NL) optical response of centro-symmetric materials are presented and evaluated with emphasis on the relationship between the macroscopic measurable quantities and the microscopic properties of photonic materials. NL refraction and NL absorption of the materials are the phenomena of major interest. The dependence of the NL refraction and NL absorption coefficients on the nature of the materials was studied as well as on the laser excitation characteristics of wavelength, intensity, spatial profile, pulse duration and pulses repetition rate. Selected experimental results are discussed and illustrated. The various techniques currently available were compared and their relative advantages and drawbacks were evaluated. Critical comparisons among established techniques provided elements to evaluate their accuracies and sensitivities with respect to novel methods that present improvements with respect to the conventional techniques.

https://iopscience.iop.org/article/10.1088/0034-4885/79/3/036401/pdf

Techniques for nonlinear optical characterization of materials: a review

A review of studies of the nonlinear refraction and nonlinear absorption of semiconductors, fullerenes, dyes, metals, crystals, and liquids (bulk samples, suspensions, solutions, embedded nanoparticles, and thin films) is presented. Some of these media are analysed as optical limiters of intense laser radiation. We present our measurements of their nonlinear refractive indices, nonlinear absorption coefficients, saturation intensities, and nonlinear susceptibilities using the laser pulses generated in various spectral and temporal ranges. Various techniques for the preparation of nanoparticles in different solvents are discussed. We also present our studies of the high-order nonlinearities of some of these media.

http://iopscience.iop.org/article/10.1088/1464-4258/7/12/004/pdf

Nonlinear refraction and nonlinear absorption of various media

We investigated As2S3 and CdS nanoparticle aqueous solutions prepared by laser ablation. Nonlinear optical characteristics of these solutions were studied by the Z-scan technique using Nd:YAG laser second harmonic radiation (λ = 532 nm, t = 55 ps). Nonlinear refractive indices, nonlinear absorption coefficients and third-order nonlinear susceptibilities of these solutions were measured. The comparison of nonlinear optical characteristics of As2S3 and CdS thin films and nanoparticle solutions was performed. It was shown that nonlinear refractive indices of As2S3 and CdS nanoparticles decreased with a growth in laser intensity. High nonlinear optical susceptibilities of such structures were attributed to size-related effects.

https://iopscience.iop.org/article/10.1088/1464-4258/5/4/317/pdf

Investigation of nonlinear refraction and nonlinear absorption of semiconductor nanoparticle solutions prepared by laser ablation

The possibility of controlling light using the nonlinear optical properties of photonic devices opens new points of view in information and communications technology applications In this Perspective, we review and analyze the potential role of metal halide perovskites in a framework different from their usual one in photovoltaic and light-emitting devices, namely, the one where they can play as nonlinear photonic materials We contextualize this new role by comparing the few extant results on their nonlinear optical properties to those of other known nonlinear materials As a result of this analysis, we provide a vision of future developments in photonics that can be expected from this new perspective on metal halide perovskites

Toward Metal Halide Perovskite Nonlinear Photonics

The nonlinear optical effects described in Chaps. 4 and 5 have to be characterized for a given material up to a certain level before they can be applied in photonics. The already wide range of applications in science, technology and medicine contains analytic aspects, questions of the structure of matter, reaction mechanisms on all time scales and the production of new states, phases or even of new matter. Thus two main questions are asked in nonlinear optics:


Which nonlinear optical effect is, for a given material suitable for a new laser analytic method (analytic tasks)?


Which nonlinear optical effect is most suitable for a desired photonic application (material and light modification tasks)?

Nonlinear Optical Spectroscopy

We present a technique for single-beam measurement of the optical
nonlinearity in GaAs for photon energies above the bandgap We
measured the real and the imaginary parts of the nonlinear refractive
index of a bulk crystal by using the change in reflection of dye laser
pulses (10 ns, 538 nm) The values obtained,
n2 = (78 ± 06) ×
10-8 cm2/W and κ2 =
(-28 ± 07) × 10-8 cm2/W, are
discussed

Measurement of Refractive Nonlinearities in GaAs Above Bandgap Energy.

We demonstrate a new experimental method which allows the measurement of the nonlinear optic index in absorptive media with great sensitivity. In this technique the reflection from a polarized Gaussian laser beam close to the Brewster angle is measured. A sensitivity enhancement factor of 30 with respect to other techniques is observed for an optical crystal, and higher values are possible to be obtained.

Sensitivity-enhanced reflection Z-scan by oblique incidence of a polarized beam

We measured the refractive-index change on a liquid sample, using
the reflection of a polarized Gaussian laser beam close to the angle of
total reflection. We applied this technique to a solution of nickel
(ii) phthalocyanine tetrasulfonated (NiPTS) in
water–ethanol (1/1 v/v), in which the nonlinearity of the
refractive index is due to optically induced thermal effects. We
show that close to the angle of total reflection the sensitivity of
this technique is four times bigger than at normal
incidence.

Measurement of refractive-index change at a liquid-solid interface close to the critical angle.

The transverse properties of squeezed light are studied for a number-squeezed edge diode laser working in an external-cavity configuration. Light noise is analyzed as a function of the transverse wave vector transmitted by a single slit at the focal plane of a short focal lens. Noise measurements obtained by opening the slit centered at the kx=0 position show a minimum squeezing at the slit center that increases up to the full-beam noise-compression. Noise is also measured by displacing a single slit of fixed width at the focal plane. The results of this wave-vector dependence are compared with a theory in which the slit is treated as a beam splitter for the incoming Hermite–Gaussian laser beam. A summation of the noise contributions at each wave vector cannot give the obtained result with the slit being open, which indicates a possible noise correlation of light with distinct wave vectors.

Transverse Fourier analysis of squeezed light in diode lasers

Summary form only given. The reflection Z-scan technique was recently suggested for the study of nonlinear effects in absorbing materials. This technique allows us to measure the modification in the reflection coefficient of a nonlinear material and to evaluate n, and /spl beta/ from this change. It is less sensitive than the transmission Z-scan technique because the beam distortion caused by the surface reflection is much smaller than the one caused by the transmission through the whole volume of the material. To overcome this small sensitivity, we suggest the use of a polarized incident beam close to Brewster angle. In this case the relative change in the reflection coefficient is increased due to the reduction in the linear term of reflection.

Ricardo Josué Horowicz

Papers

Measurement of Refractive Nonlinearities in GaAs Above Bandgap Energy.

Sensitivity-enhanced reflection Z-scan by oblique incidence of a polarized beam

Measurement of refractive-index change at a liquid-solid interface close to the critical angle.

Transverse Fourier analysis of squeezed light in diode lasers

A new technique for measuring nonlinear refractive index