| Summary: | 碩士 === 國立中正大學 === 物理所 === 97 === In this study we use single nanosecond (t=2.8ns, 532 nm) pulses as the light sources of Z-scan technique to investigate the nonlinear optical properties of Methyl Red (MR) solution wherein we change the energy (0.1uJ-40uJ) and repetition (1,2,5 and 10 Hz) rate of laser pulses to carry on these experiments. The result of repetition 10 Hz and energy 0.1uJ show MR/acetone is simple saturable absorption (SA); when pulse energy between 0.5uJ and 5.0uJ, the sample presents the simple SA in the low light intensity, and SA change to reverse saturable absorption (SA→RSA) near the beam waist, and |z| of SA→RSA increase with energy increase.When energy exceed in , Sample quality is SA→RSA→SA near the beam waist.
The result of repetition 1 Hz and energy 0.1uJ show MR/acetone is saturable absorption(SA). That is similar to the result of 0.1uJ/10 Hz and is lower transmittance. When the incidence light energy is increased to 5.0uJ, the sample still presents SA. The result different from experimental result of 5.0uJ/10 Hz on nature. That has proved that pulse to pulse accumulative effects is influenced to some extent that the hard effect of absorbs nature the sample affectionately, and continuity time of pulse to pulse accumulative effects should be between 0.1 s and 1 s.
When we impute pulse to pulse accumulative effects to mass transport and trans–cis isomerization process, we explain the contribution of these two kinds of mechanisms according to seven-energy-band model.
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