The third-order nonlinear optical properties of 1-(pyrene-1-y1)-3-(3-methylthiophene) acrylic keton named PMTAK was investigated by using Z-scan technique. The light sources for picoseconds(ps) and femtosecond(fs) Z-scan were a mode-locked Nd: YAG laser (21 ps, 532 nm,10 Hz) and an Yb: KGW based fiber laser (190 fs, 515 nm,532 nm, 20 Hz), respectively. In the two cases, reverse saturation absorption(RSA) are observed. The dynamics of the sample’s optical nonlinearity is discussed via the femtosecond time-resolved pump probe with phase object at 515nm. We believe that the molecules in excited state of particle population count is caused by two-photon absorption(TPA). The five-level theoretical model is used to analysis the optical nonlinear mechanism. Combining with the result of picosecond Z-scan experiment, a set of optical nonlinear parameters are calculated out. The femtosecond Z-scan experiment is taken to confirm these parameters. The obvious excited-state nonlinearity is found by the set of parameters. The result shows that the sample has good optical nonlinearity which indicates it has potential applications in nonlinear optics field.
<i>Meso</i>-tetrakis(4-cyanophenyl)N-confused porphyrin [NCTPP(CN)4] and its two metallized derivatives with Cu<sup>2+</sup> and Zn<sup>2+</sup> ligand in the central position of the macrocycle are synthesized and spectroscopically characterized. Their excited-state dynamics are investigated with transient absorption (TA) spectroscopy upon excitation by 190 fs laser pulses at 420 nm within their Soret band region. A global and target analysis for the TA spectra of each porphyrin is performed <i>via</i> a four-level model including singlet (S) and triplet (T) states to extract the photophysical parameters at a variety of absorption wavelengths. Furthermore the corresponding excited-state lifetimes are extracted and discussed.
The optical nonlinearities of semiconductor bulk material Indium nitride (InN) have been investigated by Reflection Z-scan technique (RZ-scan) at the wavelength of 532nm with 21ps laser pulse. Top hat beam is used in order to get high spatial quality. Different from the normal RZ-scan device, instead of moving the sample, the lens before the sample is moved along z-axis. This can guarantee the stability of the spot on the surface of the sample and the measurement accuracy. The measurement of nonlinear refraction without aperture should be tested first, and then with a small aperture nonlinear absorption coefficient is measured. The experimental results show that InN has positive nonlinear refraction and saturable absorption effect. Nonlinear refraction and absorption coefficient are obtained by fitting theoretical simulation with experimental data.
We use the time-resolved degenerated PO pump-probe technique to investigate the nonlinear absorption and nonlinear refraction dynamics of a novel porphyrin derivate, Indium-Porphyrin functionalized with polymethylmethacrylate (InPor-MMA<sub>26</sub>), dissolved in DMF at 532 nm in picosecond domain simultaneously. The results indicate that the nonlinear optical responses are induced by solution molecular excited state nonlinearity only, without the existence of two-photon absorption or Kerr refraction. Combined with five-energy-level model, all nonlinear optical parameters are determined by analyzing the experimental curves and confirmed by 4 ns Z-scan at 532 nm. The sample has a good reverse saturable absorption and reasonable positive refraction. With the proper lifetime and intersystem crossing time, this sample can be a candidate for optical limiting. The polymer attached to porphyrin directly by chemical bonds. This makes it have better homogeneity compared to physical mixing in the form of film.