Z-scan study of thermal nonlinearities in silicon naphthalocyanine-toluene solution with the excitations of the picosecond pulse train and nanosecond pulse

Abstract

Using the Z-scan technique, we studied the nonlinear absorption and refraction behaviors of a dilute toluene solution of a silicon naphthalocyanine (Si(OSi(n-hexyl)(3))(2), SiNc) at 532 nanometer with both a 2.8-nanosecond pulse and a 21-nanosecond (HW1/eM) pulse train containing 11 18-picosecond pulses 7 nanosecond apart. A thermal acoustic model and its steady-state approximation account for the heat generated by the nonradiative relaxations subsequent to the absorption. We found that when the steady-state approximation satisfactorily explained the results obtained with a 21-nanosecond pulse train, only the thermal-acoustic model fit the 2.8-nanosecond experimental results, which supports the approximation criterion established by Kovsh et al.

Towards optimized naphthalocyanines as sonochromes for photoacoustic imaging in vivo

“…Photophysical properties of the NIR absorbing dyes were measured in either spectroscopic grade toluene [56] , [88] , [89] (Scharlab, Spain) or in Milli-Q water (Merck Millipore, MA, USA). In order to solubilize the highly nonpolar Ncs in a water-based solution to mimic the in vivo environment, the Cremophor-EL (BASF, Germany) solution used by Bézière and Ntziachristos [71] was employed.…”

Study of solute migration-induced negative lensing effect in chloroaluminum phthalocyanine–ethanol

“…Note that the acoustic wave is driven by the temperature rise and the sample density that it changes contributes predominantly to the thermal lensing effect which becomes noticeable in a time comparable or longer than s ac [26]. Therefore, each 19 ps pulse with s ( s ac does not experience the thermal lensing effect generated by itself.…”

“…The thermal lensing effect, which always generates a negative lensing effect in organic solutions, is irrelevant in this study because the pulse width (s = 19 ps) is way shorter than the ns-order acoustic wave transit time (s ac ), the time it takes an acoustic wave to propagate across the beam cross-section [26], and the pulse-topulse separation s p-p is greatly longer than the millisecond-order thermal diffusivity time (s th ), the time it takes the spatially nonuniform temperature rise due to sequential photo excitation and nonradiative relaxation of the solute molecules to diminish and then disappear [16]. Note that the acoustic wave is driven by the temperature rise and the sample density that it changes contributes predominantly to the thermal lensing effect which becomes noticeable in a time comparable or longer than s ac [26].…”

Influence of blue valence absorption band on nonlinear absorption in dysprosium bisphthalocyanine studied by open aperture z-scan

“…[12,29,30]. The conventional 2PA coefficient, b0, can be evaluated by multiplication by the concentration, N 0 .…”