Saturation Effects in Z-Scan Measurements

Articles you may be interested inThird-order nonlinear optical properties of a one-and two-electron spherical quantum dot with and without a hydrogenic impurity Determination of large third-order optical nonlinearities in tetra-tert-butylphthalocyaninatogallium iodide film Ellipsometric study of the poling effect on nonlinear-optical side-chain polymers containing disperse red 1 Low band gap polythiophene derivatives synthesized using the method of Stille coupling have shown good third order nonlinear optical properties. In order to gain more insight into the structure/ property relationship in these materials, we measured the optical properties of a number of oligothiophene derivatives. In addition to linear absorption spectra, we investigated the third order nonlinear optical properties using Z-scan at a number of wavelengths. As in other conjugated oligomers, the properties depend strongly on chain length. We also observe significant dependence on the substituent type, number, and position, with strong enhancement of the oscillator strength for asymmetric substitution. The resonance nonlinear absorption shows strong saturation behavior, in general changing to induced absorption off-resonance. The nonlinear refractive indices were negative near resonance, suggesting the possibility of thermal effects. While off-resonant nonlinear refractive indices were small, in the five substances for which they could be measured, the values were found to be negative, suggesting that resonant enhancement is still playing a role.

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“…The importance of proper consideration of saturation has been considered by several authors 18 and can be seen in Fig. 7.…”

Section: B Z-scan Measurementsmentioning

confidence: 99%

Linear and third order nonlinear optical properties of substituted oligothiophenes

Keuren

Möhwald

Rozouvan

et al. 1999

The Journal of Chemical Physics

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“…The first quantitative measurement of the nonlinearity in ruby was made using an interferometric technique [10] that conclusively demonstrated the dispersive origin of the phase conjugation, since it was measured that the real part of the refractive index change was 1 order of magnitude larger than the imaginary one. From this result, it was found that the polarizability difference between excited and ground states of ruby is Δα p 1.6 × 10 −25 cm 3 , a value which was later confirmed by several experiments [4,7,[11][12][13][14][15]. For instance, the dispersive character of ruby's nonlinearity was demonstrated with the nondegenerate two-wave mixing (NDTWM) experiments of McMichael et al [11].…”

Section: Introductionmentioning

confidence: 67%

“…The experimental setup is similar to the classical Z-scan one [35], with the introduction of a chopper in order to allow time-resolved detection to eliminate parasitic linear effects [13,38]. As explained before, the refractive index change in Cr 3 -doped crystals originates from the metastable excited state, which has a polarizability different from that of the ground state.…”

Section: Z-scan Measurementsmentioning

confidence: 99%

Optically pump-induced athermal and nonresonant refractive index changes in the reference Cr-doped laser materials: Cr:GSGG and ruby

et al. 2012

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The refractive index of most ion-doped materials increases with the excited state population. This effect was studied in many laser materials, particularly those doped with Cr 3 and rare earth ions, using several techniques, such as interferometry, wave mixing, and Z-scans. This refractive index variation is athermal (has an electronic origin) and is associated with the difference in the polarizabilites of the Cr 3 ion in its excited and ground states, Δα p . The Cr 3 optical transitions in the visible domain are electric-dipole forbidden, and they have low oscillator strengths. Therefore, the major contribution to Δα p has been assigned to allowed transitions to charge transfer bands (CTBs) in the UV with strengths ∼3 orders of magnitude higher. Although this CTB model qualitatively explains the main observations, it was never quantitatively tested. In order to further investigate the physical origin of Δα p in Cr 3 -doped crystals, excited state absorption (ESA) and Z-scan measurements were thus performed in Cr:Al 2 O 3 (ruby) and Cr:GSGG. Cr:GSGG was selected because of the proximity of its 2 E and 4 T 2 emitting levels, and thus the possibility to explore the role of the spin selection rule in the ESA spectra and the resulting variations in polarizability by comparing low and room temperature data, which were never reported before. On the other hand, Cr:Al 2 O 3 (ruby) was selected because it is the only crystal for which it is possible to obtain CTB absorption data from both ground and excited states, and thus for which it is possible to check the CTB model more accurately. Thanks to these more accurate and more complete data, we came to the first conclusion that the spin selection rule does not play any significant role in the variation of the polarizability with the 2 E-4 T 2 energy mismatch. We also discovered that using the CTB model in the case of ruby would lead to a negative Δα p value, which is contrary to all refractive index variation (including Z-scan) measurements.

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“…It shows a departure from the expected asymmetric shape [9] because saturations effects distort the lens induced by nonlinear processes. In order to treat this situation in a rigorous way, the Hankel transformation method should be employed to deal with the light propagation in the case where the induced phase is not Gaussian [14]. This cumbersome analysis is out of the scope of the present work.…”

Section: Resultsmentioning

confidence: 99%

Dynamic saturable optical nonlinearities in free base tetrapyridylporphyrin

Neto

Boni

Rodrigues

et al. 2003

J. Porphyrins Phthalocyanines

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Dynamic optical nonlinearities in free base tetrapyridylporphyrin (H 2 TPyP) solutions were investigated at 532 nm with the Z-scan technique. We observed a reverse saturable absorption process that was found to have a fast contribution related to the singlet population and a slow accumulative contribution arising from the triplet population. The optical excitations and subsequent relaxations can be interpreted with a five-energy-level diagram that allows determination of the excited states photophysical parameters such as triplet and singlet absorption cross-sections and the intersystem crossing time.

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Saturation Effects in Z-Scan Measurements

Cited by 48 publications

References 11 publications

Linear and third order nonlinear optical properties of substituted oligothiophenes

Linear and third order nonlinear optical properties of substituted oligothiophenes

Optically pump-induced athermal and nonresonant refractive index changes in the reference Cr-doped laser materials: Cr:GSGG and ruby

Dynamic saturable optical nonlinearities in free base tetrapyridylporphyrin

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