Z-scan technique

The Z-scan technique, first introduced in 1989 [64, 65], is a sensitive single-beam technique to determine the nonlinear absorption and nonlinear refraction of materials independently from their fluorescence properties. The simplicity of separating the real and imaginary parts of the nonlinearity, corresponding to nonlinear refraction and absorption processes, makes the Z-scan the most widely used technique to measure these nonlinear properties however, it does not automatically differentiate the physical processes leading to the nonlinear responses. 

For 2PA or ESA spectral measurements, it is necessary to use tunable laser sources where optical parametric oscillators/amplifiers (OPOs/OPAs) are extensively used for nonlinear optical measurements. An alternative approach, which overcomes the need of expensive and misalignment prone OPO/OPA sources, is the use of an intense femtosecond white-light continuum (WLC) for Z-scan measurements [71,72]. Balu et al. have developed the WLC Z-scan technique by generating a strong WLC in krypton gas, allowing for a rapid characterization of the nonlinear absorption and refraction spectra in the range of 400-800 nm [72]. 

The main advantage of the usual Z-scan technique is that this method allows for a direct measurement of the nonlinearity, not requiring the use of reference samples, and thus minimizing experimental errors. On the other hand, the necessity of... 

In the linear absorption measurements of these photolabile compoxmds, there is a concern that during the measurement of the 2 PA cross sections the photoinitiators may photodecompose, which would in turn affect the observed cross section, especially when the Z-scan technique is used. The Z-... 

The tables in this section contain data from approximately 35 research papers that have mostly employed THG, DFWM, or Z-scan techniques to measure the third-order hyperpolarizabilities of organometallic complexes. 

A series of solution-processible and tractable polymetallaynes of Pt and their mixed-metal analogues were demonstrated to be excellent OPL materials to nanosecond laser pulses at 532 nm, with optimized optical transparency/ nonlinearity trade-offs. The optical-limiting behavior of selected platinum(II) polyynes was investigated by the Z-scan technique. Polyynes 19, 21, 22, 27, 29,... 

If intrinsic two-photon absorption cross-sections are the subject of investigation short pulses (ps or fs) should be used and two-photon fluorescence (see below) should be measured to verify the Independence of the TPA process. Most often, two-photon absorption is measured either with the Z-scan technique (see above) or with the nonlinear transmission method [38]. 

Kyoung, M., Lee. M. Nonlinear absorption and refractive index measurements of silver nanorods by the Z-scan technique. Opt. Commun. 171, 145-148 (1999)... 

Even if it is out of the scope of the present chapter, it is worth mentioning that the third-order NLO behavior of SubPes-based condensed phases has been also studied. Resonant and off-resonant third-order NLO properties of spin-coated films of SubPc 17 were determined via Z-scan technique [80]. THG experiments have been also performed on sublimated boron SubPc 2 thin films [81],... 

All complexes are optically transparent at the fundamental frequency corresponding to the measurement wavelength of 800 nm. Measured in THF by the Z-scan technique. Results are referenced to the nonlinear refractive index of silica 2 = 3 x lO- cm W". ... 

The nonlinear optical properties in solution of selected functionalized PDAs, described herein, have also been evaluated by means of the z-scan technique. Off resonance studies (at 705 nm) show that nonlinear refraction is only comparable to that of the solvent for these dilute solutions, but that nonlinear absorption, characterized by p values, varies significantly, with the nature of the side-chains. O It can be inferred that if bulk films of these PDAs possess suitable nonresonant nonlinear refractive properties for optical devices, modification of side-chain structure can reduce the magnitude of undesirable two photon absorption. 

TPA can be measured by the transmission method or by the Z-scan technique. Moreover, two-photon fluorescence can serve to measure TPA absorption cross-sections, provided that a fluorescent excited state is reached by TPA. In nonlinear... 

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