Measurement of nondegenerate nonlinearities using a two-color Z scan

Abstract

A simple dual-wavelength (two-color) Z-scan geometry is demonstrated for measuring nonlinearities at frequency omega(p) owing to the presence of light at omega(e). This technique gives the nondegenerate two-photon absorption (2PA) coefficient beta(omega(p); omega(e)) and the nondegenerate nonlinear refractive index n(2)(omega(p); omega(e)), i.e., cross-phase modulation. We demonstrate this technique on CS(2) for n(2) and on ZnSe where 2PA and n(2) are present simultaneously.

Ultrafast nonresonant response of TiO2 nanostructured films

“…Single beam and two-color variations of this technique were developed by Gardecki et al 12 and Sheikbahae and co-workers. [13][14][15] In the so-called "position-sensitive Kerr lens" technique, developed by Simon et al, the deviation of a probe beam in the pumpinduced lens is measured by comparing the detected light in the two panels of a dual diode as a function of probe delay. 16,17 More recently, Gardecki et al 12 and Tokmakoff and co-workers 18,19 showed that placing an aperture in the probe beam path after the sample and adjusting the relative polarizations of the pump and probe beams allows to make a direct heterodyned detection of individual elements of the response function tensor, and developed an unified theory for all the TL techniques.…”

Sensitivity of Z-scan using diffraction efficiency

“…The sensitivity of this method increases with decreasing aperture size allowing to sense a nonlinear wave front distortion as small as λ/250. Later, several variations of the Z-scan method have been developed in order to improve this sensitivity [3][4][5][6][7][8][9]. Particularly, the need to characterize thin film samples has motivated the development of the eclipsing Z-scan (EZ-scan) where the disk is used instead of the aperture [10] and the transmittance of the beam around this obscuration is measured.…”

Finite thickness lens model for self-focusing (defocusing) in Kerr medium

“…Self-focusing in a thin film Kerr medium is a well-known nonlinear optical phenomenon and has been extensively studied experimentally and theoretically [1][2][3][4][5][6][7][8][9][10][11][12][13]. Based on the aberration-less theory of self-focusing, in which the beam is assumed to maintain its Gaussian profile during propagation in the Kerr medium, a nonlinear ABCD matrix has been proposed to deal with the Gaussian beam propagation through a nonlinear thin medium.…”