Measurement Of Nonlinear Optical Susceptibility Research Articles

Spectroscopy of laser-induced autoionizing nonlinear resonances in atomic systems

Efficient harmonic generation at laser-induced autoionizing state in continuum, were observed for the first time by our laboratory [1,2,3]. In this paper, nonlinear frequency mixing in alkali metal vapors at induced continuum structure in Na, are studied in detail. Besides, measurement of nonlinear optical susceptibility at induced autoionizing resonance, is performed. Tunable ultraviolet radiations by four-photon processes near induced resonances are obtained. Estimations of the real and imaginary parts of the nonlinearities, are estimated. We will specially note, that the resonant photoabsorption of ions is experimentally investigated since it gives information about the autoionizing states, which is impossible to obtain on the base only of the emission spectra. We use also laser inducing for obtaining of powerful radiation source in VUV. Thus, many actual problems as the selective impact on matter, laser photochemistry and laser isotope separation are connected directly with the induced autoionizing nonlinear resonances. The main interest is to control the spectral characteristics of continuum. The discrete level from the continuum structure leads to appearance of asymmetrical autoionizing resonance onto the background of the broad-band absorption line.

Third-harmonic generation measurement of nonlinear optical susceptibility χ^(3) of Ge-Ga-Sb-S chalcogenide glasses proposed for highly nonlinear photonic fibers

We measured the nonlinear optical susceptibility χ(3) of some Ge-Ga-Sb-S chalcogenide glasses feasible for the fabrication of highly nonlinear photonic crystal fibers. The χ(3) values of Ge17Ga4Sb10S69, Ge20Ga5Sb10S65, and Ge20Ga5Sb6S69 glasses were found to be 3.5, 2.6, and 1.8×10−19m2/V2 (6.3, 4.6, and 3.2×10−12esu, where “esu” stands for electrostatic unit) at the fundamental wavelength λ=1.9μm, i.e., 227, 167, and 117 times higher than that of standard silica [1.55×10−21m2/V2 (2.79×10−14esu)]. Their nonlinear refractive indices n2 were then obtained as 1.8, 1.3, and 1×10−17m2/W (5.1, 3.7, and 2.7×10−11esu). They are ∼78, 56, and 43% of n2=2.3×10−17m2/W (7×10−11esu) of the As2S3 glass used as the chalcogenide glass reference.

Time-resolved absolute interferometric measurement of third-order nonlinear-optical susceptibilities

A modified Mach–Zehnder interferometer has been built for measurement of nonlinear-optical susceptibilities in bulk materials. Both slow- and fast-intensity-dependent refractive-index changes can be measured in absolute value, with femtosecond time resolution, high sensitivity, and precision, by means of a new fringe-locking technique. Results on fast nonlinearities of CS2 liquid and glasses are presented.

Nonlinear optical susceptibility measurement at an autoionizing-like resonance in atoms

The first experimental measurement of nonlinear optical susceptibilities at a laser-induced resonance in the atomic continuum is reported. Raman amplification efficiency as well as polarization anisotropy are investigated by scanning the probe frequency near the autoionizing-like resonance. Tunable ultraviolet radiations by four-photon processes in sodium vapour near the induced resonances are obtained. Estimations of the real and imaginary parts of the nonlinearities and also of their moduli are presented.

Absolute measurement of the second-harmonic generation nonlinear susceptibility of tellurium at 28.0 µm

The second-harmonic generation nonlinear optical susceptibility of trigonal tellurium has been measured at 28.0 μm by the phase-matching technique. The value obtained was <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">|d_{11}| = (5.7 \pm 1.9) \cdot 10^{-10}</tex> m/V in MKS units. This value establishes the longest wavelength "standard" for the measurement of nonlinear optical susceptibilities by comparative techniques. Experimental details and data are given to justify the quoted uncertainty.